--- type: Whitepaper title: "The Masks We (Think We) Wear: Privacy Threats of Browser-Extension Wallets in the Web3 Ecosystem" description: "A browser-extension wallet is both a blockchain client and an identity provider, and five privacy threats follow from doing both in a page. Measuring 85 Chrome wallets covering 35.16M users: routine RPC calls link a user's separate addresses, most Ethereum wallets keep exposing an address after its permission is revoked, and many inject their provider into cross-origin iframes." resource: "https://petsymposium.org/popets/2026/popets-2026-0094.pdf" tags: [whitepaper, webseclist-reference, proceedings-on-privacy-enhancing-technol, browser-extension, blockchain, deanonymization, info-leak, measurement-study, iframe, browser-fingerprinting] generated: by: webseclist-refs/1 at: "2026-08-19T00:32:08+00:00" status: stable stale_after: 2027-08-19 sources: - id: original resource: "https://petsymposium.org/popets/2026/popets-2026-0094.pdf" title: "The Masks We (Think We) Wear: Privacy Threats of Browser-Extension Wallets in the Web3 Ecosystem" author: Weihong Wang, Yana Dimova, Victor Vansteenkiste, Tom Van Goethem, Tom Van Cutsem also_at: [] authors: - Weihong Wang - Yana Dimova - Victor Vansteenkiste - Tom Van Goethem - Tom Van Cutsem canonical_url: "" cited_by: - "2026-ai.md:64" commit: "" content_sha256: 70d0e02dd82666be079710ff280e855f5f8b25d36640094d1609f88b24b2dc51 depth: full depth_reason: default kind: whitepaper language: "" licence: unknown original_url: "https://petsymposium.org/popets/2026/popets-2026-0094.pdf" published: "" publisher: Proceedings on Privacy Enhancing Technologies publisher_english: "" raw_sha256: abd009ff2de70abedf9ba5f8e1876fda1ddd0668fcb7b4d15dece9b210e2ec76 retrieved_from: "https://petsymposium.org/popets/2026/popets-2026-0094.pdf" retrieved_kind: live retrieved_utc: "2026-08-19T00:32:08+00:00" slug: masks-we-think-we-wear-privacy-threats-browser-extension-wallets-web3-ecosystem snapshot: "" title_english: "" translation_file: "" translation_of: "" --- # The Masks We (Think We) Wear: Privacy Threats of Browser-Extension Wallets in the Web3 Ecosystem **The Masks We (Think We) Wear: Privacy Threats of Browser-Extension Wallets in the Web3 Ecosystem** - Weihong Wang, Yana Dimova, Victor Vansteenkiste, Tom Van Goethem, Tom Van Cutsem, Proceedings on Privacy Enhancing Technologies. - Published: date not stated - Original: - Preserved from: https://petsymposium.org/popets/2026/popets-2026-0094.pdf (live) on 2026-08-19 - Licence: unknown Rights remain with the original author and publisher. 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The Masks We (Think We) Wear: Privacy Threats of Browser-Extension Wallets in the Web3 Ecosystem Weihong Wang Yana Dimova Victor Vansteenkiste DistriNet, KU Leuven DistriNet, KU Leuven DistriNet, KU Leuven Leuven, Belgium Leuven, Belgium Leuven, Belgium weihong.wang@kuleuven.be yana.dimova@kuleuven.be victor.vansteenkiste@hotmail.com Tom Van Goethem Tom Van Cutsem DistriNet, KU Leuven DistriNet, KU Leuven Leuven, Belgium Leuven, Belgium tom.vangoethem@kuleuven.be tom.vancutsem@kuleuven.be Abstract 1 Introduction Cryptocurrency wallets are the primary interface for managing Browser-extension wallets such as MetaMask form a common entry pseudonymous blockchain addresses, viewing balances, and inter- point to interact with so-called “Web3” or “decentralized applica- acting with Web3 applications. Although users typically assume tions” (dApps) in the browser. As illustrated in Figure 1, these that their addresses remain independent of each other unless inten- wallets typically serve a dual role. First, they operate as a finan- tionally revealed, modern wallets routinely communicate with both cial interface, querying blockchain nodes (or the wallet’s own blockchain infrastructure and decentralized applications (dApps), backend) for balances and other on-chain data associated with the generating network-side and web-side signals that may undermine user’s addresses. Second, they act as an identity provider: when a this assumption. dApp requests access, the wallet lets the user select which address In this paper, we identify and formalize five privacy threats that to reveal so the dApp can authenticate the session. The wallet thus arise directly from wallets interacting with the network and the coordinates the user’s interactions with blockchain infrastructure web browser. Using large-scale dynamic measurements of 85 of on the one hand, and dApp front-ends on the other hand. the most popular Chrome Web Store browser-extension wallets (representing 35.16 million users), we observe that routine remote procedure call (RPC) operations leak structural links between a user’s addresses; that the majority of Ethereum wallets implement permission revocation inconsistently and continue to expose pre- viously revoked addresses across sessions; and that many wallets inject their provider interfaces into cross-origin iframes, enabling passive cross-site tracking beyond dApps and potentially real-world identity deanonymization without user interaction. Taken together, our results show that these wallet behaviors leak sensitive information that can be used to link multiple addresses Figure 1: A wallet’s two roles: financial interfaces (showing to the same user, track wallet users across sessions and sites, and user balances) and identity providers (login). connect their browsing activity to their on-chain wealth. Each blockchain address is a persistent public identifier. Its as- We discuss practical mitigations and show that many of these sociated on-chain wealth, complete transaction history, token and threats can be substantially reduced through improved wallet imple- NFT holdings, and interactions with smart contracts, is visible mentation, stronger privacy considerations in ecosystem standards, to anyone who learns the address. Because a single address and stricter controls over provider exposure. Our results highlight reveals such a detailed record of activity, users often spread their the need for standardized, privacy-preserving wallet architectures actions across multiple addresses to separate identities, reduce risk, and provide actionable guidance for strengthening user privacy in or avoid creating a single public on-chain profile. the emerging Web3 ecosystem. This separation is only effective if the addresses remain unlinked. Once two addresses are associated, their histories can be combined, Keywords allowing external parties to infer the user’s overall asset ownership, Browser-Extensions, Blockchain Wallets, Web Tracking, User Pri- behavioral patterns, and financial status, increasing the risk of vacy targeted phishing or other unwanted attention. Although many users treat addresses as separate pseudonyms This work is licensed under the Creative Commons Attribu- tion 4.0 International License. To view a copy of this license unless they explicitly disclose a connection, prior work [2, 19, 22, 32] visit https://creativecommons.org/licenses/by/4.0/ or send a has shown that this assumption does not fully hold, since addresses letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA. can often be linked through on-chain graph analysis. Proceedings on Privacy Enhancing Technologies 2026(3), 523–537 © 2026 Copyright held by the owner/author(s). Our study shows that the privacy risks are even broader than https://doi.org/10.56553/popets-2026-0094 what can be inferred from on-chain activity alone. As the main 523 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. entry point to Web3, wallets introduce additional privacy risks. examines their impact. We discuss mitigation strategies in Section 6, Because they mediate both blockchain data queries and identity related work in Section 7 and conclude in Section 8. We release flows, wallets generate network-level and web-level signals that artifacts and a demo in Section 9, and document our responsible leak wallet addresses and enable address linkability in previously disclosure process in Section 10. undocumented ways. While earlier work has shown that wallets leak addresses to external endpoints [29], we show that routine 2 Background wallet behavior, including background network traffic and the ex- posure of provider interfaces to web pages, can reveal additional This section introduces how browser-extension wallets function sensitive information about users and their addresses. By analyzing and how decentralized applications interact with them. We describe both network-side and web-side data flows, we identify five classes the primary roles of the wallets, how they are detected by dApps, of privacy threats: and how permissions governing these interactions are managed. • Network-side #1: network-level address linkability; 2.1 Roles of Browser-Extension Wallets • Web-side #1: wallet fingerprinting; • Web-side #2: cross-session tracking and address clustering within a single dApp; 2.1.1 Wallet as a Financial Interface. When functioning as • Web-side #3: cross-site tracking and address clustering across a lightweight financial interface, a wallet must routinely fetch multiple dApps; on-chain data such as account balances, token metadata, trans- • Web-side #4: tracking and deanonymization beyond dApps. action history, or gas prices. For example, to display a balance, a wallet issues an RPC (remote procedure call) request such as: Our measurements show that these privacy threats are preva- eth_getBalance(address). Any blockchain node that exposes an RPC lent across the current Web3 ecosystem rather than isolated to a endpoint can respond to these queries. few misconfigured wallets. Across the 85 wallets in our dataset, Because running a full blockchain node is resource-intensive, representing 35.16 million Chrome Web Store users, we observe most wallet developers rely on third-party node providers (e.g. substantial exposure at both the network and web layers. At the Infura, Alchemy, Ankr, QuickNode) rather than operating their own network layer, 17 wallets leak structural linkability signals, affect- infrastructure. Some wallets allow users to configure a custom RPC ing 23.0 million users (65.4%). At the web layer, 36 wallets, covering endpoint, but many use a fixed provider chosen by the developers. 82% of the total user base, are detectable through our new fin- gerprinting vector. More importantly, among these 36 wallets, 22 2.1.2 Wallet as an Identity Provider. A browser-extension wal- fail to correctly revoke permissions when users log out of a dApp let can also act as an identity provider for dApps, similar to logging and continue to expose previously granted but revoked addresses. into a website with Google. Google stores the account, and the web- This persistent exposure can be exploited by third-party trackers site receives only the identity information it needs. In Web3, the to link users across sessions and dApps. Additionally, 23 of these wallet holds the user’s private keys and manages their blockchain wallets inject their provider interfaces into cross-origin iframes, accounts, and the dApp receives the public address that the wallet allowing third-party trackers on non-dApp sites to obtain a user’s discloses only after showing a confirmation prompt to the user. wallet address without any explicit user interaction. This can link Once the address is provided, the dApp can independently look a user’s browsing activity to their on-chain wealth and, in some up public on-chain data (such as balances, history, or token hold- cases, facilitate deanonymization. ings). However, any action that moves funds or signs a transaction Our contributions are as follows: still requires an explicit confirmation from the user through the • We perform the first systematic analysis of privacy risks in wallet interface. browser-extension wallets across both the network and web Wallets store permission and connection state locally within layers, and identify five privacy threats with ecosystem-wide the extension environment, e.g., which dApps have been granted impact. access to which accounts. This local state determines how the wallet • We conduct a large-scale empirical study of network traffic responds to future wallet provider API calls. and web-side data flows from 85 widely used Chrome Web Store wallet extensions. 2.2 How dApps Discover Wallets • We show that these threats are widespread in practice, and For a dApp to request access to a user’s accounts, it must first detect trace two major sources of exposure to incomplete permis- the browser’s available wallets. In Ethereum (the most widely used sion revocation and unsafe provider injection into cross- blockchain for dApps), wallets can be detected as follows: origin iframes. 2.2.1 EIP-1193 (Legacy Provider Injection). Before October • We propose and discuss mitigations for all five threats, in- 2023, browser-extension wallets generally exposed their Ethereum cluding a script-level access-controlled localStorage design provider by injecting an EIP1 -1193-compliant [33] object into the to prevent wallet-based tracking. webpage’s global variable window.ethereum. As the ecosystem The remainder of this paper is organized as follows. Section 2 pro- grew and users started using multiple wallets at the same time, this vides background on browser-extension wallets. Section 3 details became problematic. Each wallet injected its own provider object, our methodology. Section 4 defines and evaluates network-side pri- 1 EIP stands for Ethereum Improvement Proposal, the standardization process for vacy threats, while Section 5 introduces four web-side threats and Ethereum interfaces and protocols. 524 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) and the last one to load would overwrite the others. This made it • MetaMask defines a revocation method in its MIP-2 pro- difficult for dApp developers to detect which wallet the user wanted posal [23]. This method, named wallet_revokePermissions, to connect or to let users choose among several installed wallets. allows a dApp to request that the wallet revokes permissions previously granted to that dApp. Some other wallets follow 2.2.2 EIP-6963 (Modern Multi-Wallet Discovery). To support it and also support this method. the coexistence of multiple wallet extensions, EIP-6963 [14] was pro- • Many wallets expose no revocation API to dApps, so logging posed, which introduced a discovery mechanism in which wallets out of a dApp does not revoke previously granted permis- announce themselves without competing over window.ethereum. sions. In such cases, permissions may persist until the user Instead of directly overwriting a single global object, wallets dis- manually removes them for each site through wallet-side UI, patch an eip6963:announceProvider event containing two fields: such as a “Connected Sites” or “Permissions” screen. • info: metadata about the wallet (e.g., name and icon), Because no EIP currently defines a uniform revocation workflow, • provider: the wallet provider object. the persistence and removal of permissions remain inconsistent A dApp listens for these announcements and can present a UI across wallet implementations. allowing the user to select a wallet. The eip6963:requestProvider event was introduced in EIP6963, which prompts all installed wal- lets to re-announce themselves. This enables reliable multi-wallet 3 Methodology detection and avoids conflicts caused by legacy provider injection. 3.1 Measurement Goals Our study focuses on two adversaries that can observe different 2.3 Wallets Permissions and Revocation aspects of a browser-extension wallet’s behavior: (1) network end- A wallet must also control which dApps may access the user’s point servers, and (2) web-based adversaries embedded on web- wallet addresses. This permission model, standardized in Ethereum pages. Our measurement goals reflect what each adversary model through EIP-2255 [12], operates entirely in the browser and governs can see. how a dApp requests access to identity-related information. 3.1.1 Network-Side Measurement Goals. Any endpoint the 2.3.1 EIP-2255 (Wallet Permissions System). EIP-2255 defines wallet connects to can see all outbound traffic initiated by a wal- a capability-based permission system for wallet-dApp communi- let extension to that endpoint. Hence, our goal is to measure the cation. These permission checks occur entirely in the browser be- information at the network layer, including: tween the dApp and the wallet provider. Each method exposed by the wallet provider to the dApp is • whether these requests included wallet-related information, classified as either restricted or unrestricted. A restricted method • which third-party endpoints receive these address-bearing is one that accesses a capability available only after the user has requests, explicitly approved it. An unrestricted method does not itself require • whether the overall traffic patterns reveal relationships be- prior permission, but calling it may trigger a wallet prompt asking tween multiple accounts in the same wallet. the user to grant permission for a restricted method. 3.1.2 Web-Side Measurement Goals. A web-based adversary • eth_accounts: restricted. It returns either an empty array operates through third-party scripts embedded on a webpage. This or only the accounts the caller is permitted to access by the adversary’s visibility arises from the wallet’s web-facing provider user. APIs and events. Our goal is to measure what information becomes • eth_requestAccounts: unrestricted. Calling this method accessible to such an adversary at different stages of wallet usage: triggers a wallet prompt asking the user to approve or reject account access for a given dApp. Once approved, this • Installed but not connected: whether the presence of a permission causes later calls to eth_accounts from the dApp wallet can be discovered, to return the user-authorized accounts until the permission • Connected: what provider APIs, events, or address data is revoked by the user. become available when a wallet connects to a dApp, • Revoked: what residual information remains accessible after 2.3.2 How Wallets Store Permission Information. Wallets the dApp requests permission revocation. record which addresses a given website origin is allowed to access using a per-origin authorization state internally, typically in the 3.1.3 Methodological Structure. These goals motivate two com- extension-managed storage. When the webpage calls eth_accounts, plementary measurement frameworks: the wallet checks this record: If permission exists, the wallet returns the previously authorized addresses. If not, it returns an empty ar- • a Network Request Interceptor framework, improved ray. EIP-2255 does not define expiration, so wallets differ in how from the request-interception approach of Torres et al. [29], long this state persists. which detects leakage of addresses in the wallet’s outbound network traffic. We also extended it to support our measure- 2.3.3 Lack of a Standard for Permission Revocation. While ment scope. EIP-2255 specifies how permissions are requested and granted, it • a Web Exposure framework that observes the wallet provider does not standardize any mechanism by which websites can revoke interface to detect what data becomes observable to third- them. As a result, wallet implementations differ substantially: party scripts throughout different stages. 525 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. 3.2 Datasets Construction activity from extension components (type service_worker and Our measurements require three types of datasets: (i) source-code background_page). Our modification adds these two extra target of browser-extension wallets, to characterize network- and web- types to the interception logic and writes their network events to side behavior across the ecosystem; (ii) decentralized applications separate log files. The rest of the data-collection process remains (dApps), to observe real-world wallet–dApp interactions; and (iii) unchanged. third-party analytics and tracking domains. To simulate a real user with multiple addresses in one wallet, the framework records all addresses created during setup, so the ad- 3.2.1 Torres et al. Wallet Dataset. For our reproduction study of dresses can be reused consistently across experiments and analysis. Torres et al.’s results, we used their dataset of 100 wallet extensions, which contains the exact versions they analyzed in 2023. We refer 3.3.3 Account Funding. We transferred a small amount of ETH to this data set as Torres-2023/100. (≈ 1 USD) to the primary two test addresses. This lets us verify We also downloaded the latest available versions of these same that the wallet correctly displays balances, and that it is actively 100 wallets from the Chrome Web Store as of November 2025. We querying external services for blockchain data. Based on this check, refer to this updated dataset as Torres-2025/100. we assigned wallets to three categories: • Broken: the extension could not be installed, initialized, or 3.2.2 CWS-10K/85 (85 Chrome Web Store (CWS) Wallets opened. with >10K Users). Because more than 25% of the extensions in the • Partially functional: the extension loaded and appeared Torres’ dataset are no longer available on the Chrome Web Store operational, but did not display the correct balance. and the list is outdated, we crawled a fresh list of wallet extensions • Fully functional: the extension initialized successfully and directly from the store. Using the keywords “crypto wallet”, “web3 displayed the expected balance. blockchain wallet”, and “web3 wallet”, we collected a total of 198 entries and kept only those with more than 10K users on the Chrome Wallets classified as partially functional that also produced no Web Store (November 2025). This filtering step produced a dataset outbound traffic to external services were labeled excluded, to- of 85 modern wallets, which we refer to as CWS-10K/85. gether with the broken wallets, omitted from subsequent analysis. 3.2.3 dApp Dataset (30 Popular Ethereum dApps). To under- 3.3.4 Measurement Procedure. Torres et al.’s original study stand how real dApps interact with wallets, we collected the 30 relies on Chrome browser profiles. For each of the 100 wallet exten- most popular Ethereum dApps from DappRadar’s Ethereum cat- sions, they manually set up the wallet, created a single test account, egory [9] as of 14 November 2025. We only included dApps with and saved the resulting browser profile. During testing, Puppeteer functional frontends that could connect to an Ethereum-compatible reloaded these profiles and ran a routine that randomly clicked wallet. The goal of this dataset is not exhaustive coverage, but to up to ten UI elements or stopped after sixty seconds. During this provide a representative set of real sites through which to observe period, the framework recorded all outgoing traffic. connection flows, account requests, and revocation behavior. We followed the same experimental procedure, but performed all measurements using our improved request interceptor framework. 3.2.4 The List of Analytics Sites. We compiled a small list of During wallet setup, if the extension prompted for telemetry or common third-party analytics and tracking domains using publicly analytics data collection, we explicitly declined such requests when- documented providers. The full list of 21 domains used in our ever possible. We first ran these experiments on the Torres-2023/100 classification is provided in Appendix A. dataset to compare our measurements with the original study and quantify how much traffic the baseline framework missed. We re- 3.3 Network Request Interceptor Framework peated these experiments on the Torres-2025/100 and CWS-10K/85 3.3.1 Baseline Framework (Torres et al.) The Puppeteer-based datasets to evaluate whether these blind spots persist in current request interceptor framework, developed by Torres et al., 2 attaches wallet versions. network listeners to webpage contexts, allowing us to observe the Specifically, we applied the multi-account setup only to the CWS- full HTTP and WebSocket request parameters before TLS encryp- 10K/85 dataset. Each wallet was initiated with three accounts, and tion is applied. However, the framework only monitors requests their addresses were recorded. The subsequent traffic-capture pro- from browser tabs and does not capture requests originating from cedure was identical to the single-account measurements. Chrome extension components such as background pages (Chrome Manifest V2) or service workers (Chrome Manifest V3) [13, 27]. Be- 3.4 Web Exposure Framework cause modern wallet extensions often issue background traffic from these components, such requests appear “silent” to the baseline framework even while the extension is actively communicating 3.4.1 Framework Design. We developed a Playwright-based with external endpoints. framework to evaluate wallet discovery via EIP-6963 events and the implementation of permission requests, revocation, and recon- 3.3.2 Improved Request Interceptor Framework. To address nection by wallets. The framework performs four actions for each the blind spots, we extended the baseline framework to monitor not wallet: only browser tabs (Puppeteer targets of type page), but also network (1) Discover: discovers a wallet, 2 The Puppeteer-based request interceptor framework by Torres et al.: https://github. (2) Connect: triggers a wallet connection request from dApp, com/christoftorres/Web3-Privacy/tree/main/framework/request-interceptor (3) Disconnect: requests permission revocation from dApp, 526 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) (4) Evaluate: checks what address information the dApp can post-revocation state. The same procedure is applied both to our still access afterward. minimal testing dApp and to the 30 real-world Ethereum dApps. To create a controlled testing environment, we built a minimal test dApp with only two buttons: a Connect button to trigger 3.5 Ethical Principles eth_requestAccounts after a wallet is discovered, and a Discon- All experiments were conducted using test accounts and isolated nect button to trigger wallet_revokePermissions. During each browser profiles. No real users or personal data were ever collected, test, we instrumented the page to record all wallet-dApp permission observed, or shared. interactions: • the wallet provider API calls (eth_requestAccounts, 4 Network-Side Threats and Results eth_accounts, wallet_revokePermissions, etc.), This section examines the privacy risks that arise from wallet- • the address information accessible by the dApp through initiated network traffic. We begin by defining the network-side calling eth_accounts after disconnect. threat model and the information available to adversaries through standard RPC (Remote Procedure Call) communication. We then de- We also applied the same instrumentation to 30 real Ethereum scribe the resulting privacy threat and present the empirical results dApps to understand how modern sites behave in practice. For observed across the three datasets using our improved request- these real-world dApps, we additionally recorded: interceptor framework. • localStorage and cookies modifications, • all outbound dApp requests to external services. 4.1 Threat Model These additional real-world samples help reveal broader dApp The adversary does not break cryptography, compromise private interaction patterns in wallet discovery and connection. keys, or interfere with normal wallet functionality, but exploits in- formation gained from standard wallet-initiated network requests. 3.4.2 Measurement Procedure. Before running experiments, We consider as the network-side adversary any external ser- each wallet in the CWS-10K/85 dataset was set up once to create a vice endpoint that receives the wallet’s HTTPS requests during clean browser profile. Our framework supports partial automation normal operation. These endpoints fall into two categories: (1) for this task, for example, detecting input fields for seed phrases wallet vendor–operated backends, which handle or forward the or passwords, but many wallets present non-standard onboarding requests to other services; and (2) non-vendor-operated domains, flows. Because automation is not the focus of this work, we use including node providers and RPC endpoints (e.g., Infura, Alchemy, automated steps when they succeed and fall back to manual in- Etherscan), which process blockchain state queries from wallets teraction when needed. Each experiment starts from a copy of the (see Appendix B for representative domains), as well as analytics corresponding clean profile so that the wallet always begins in a or telemetry services that collect usage or diagnostic information fresh state, with no existing permissions or prior connections. For about wallet activity (see Appendix A). each wallet-dApp interaction, the framework performs the follow- Because these servers receive the decrypted HTTPS request, they ing steps: have full visibility into the plaintext request body and can observe: Detecting: We first attempt to detect wallets using the EIP-6963 • the full request payload, including wallet addresses, discovery workflow by dispatching eip6963:requestProvider and • the ordering and timing of consecutive requests, collecting the provider’s name. • client metadata such as IP address and user agent. The adversary responds correctly to queries but may analyze Connecting: the content and structure of incoming requests to infer information (1) Unlock the wallet. about the user. (2) Load the testing dApp. (3) Identify and click a “Connect” button on the page. 4.2 Threat#1: Network-Side Address Linkability (4) Wait for the wallet’s connection prompt to appear. (5) (Inside the wallet UI) Select the test account. Adversary: An external service endpoint that receives address- (6) (Inside the wallet UI) Appprove the connection request using bearing RPC requests from the wallet. the wallet’s confirmation interface. Source of Leakage: Multiple wallet-initiated calls whose payloads or timing reveal structural relationships between addresses. Disconnecting: Browser-extension wallets routinely automatically initiate back- (1) Identify and click a “Disconnect” button on the page. ground RPC requests (for balances, nonces, etc.) which include one (2) Trigger the wallet_revokePermissions request from the or more wallet addresses in the JSON-RPC payload. Because an dApp. external service endpoint is the TLS termination point, it receives Because wallet and dApp interfaces for these steps vary widely, these requests in plaintext and can observe the addresses, the order- some interactions can be handled automatically by the framework ing of requests, and sometimes contact analytics and send sensitive while others require manual clicking. information. After the disconnect step, the framework reloads the page and We consider the privacy threat that arises when such requests queries eth_accounts to record what information remains accessi- reveal that multiple blockchain addresses belong to the same wallet ble to page-executed scripts. The returned value is recorded as the instance. Two observable patterns enable this inference: 527 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. Metric Torres- Torres- CWS- “valid third-party” domains.3 To enable a fair comparison, we apply 2023/100 2025/100 10K/85 the same filtering and then measure the additional non-vendor Number of Wallets Leak Addresses exposure captured by our instrumentation. In Torres-2023/100, 12 wallets leaked addresses to non-vendor To any endpoints 42 43 57 domains from the page context. Seven of these overlap with the 13 To analytics endpoints 0 2 3 To telemetry endpoints 4 4 4 wallets identified in the original study. When extension background contexts background_page and service_worker are included, an Third-Party Domains Receiving Addresses additional 25 wallets leaked addresses to non-vendor domains, rep- Total domains receiving addresses 64 80 113 resenting a substantial increase in observable third-party exposure. Contacted by only one wallet 53 63 99 To assess whether this measurement gap still exists two years Percentage contacted by only one wallet 82.8% 78.8% 87.6% later, we apply the same procedure to Torres-2025/100. After vendor (53/64) (63/80) (99/113) filtering, 18 wallets leaked addresses to non-vendor domains from Analytics / Telemetry Presence in Wallets the page context, while 22 did so from background contexts. Across Wallets embedding analytics/telemetry 14/42 16/43 26/57 both datasets, background activity missed by the baseline frame- (33.3%) (37.2%) (45.6%) work remains a major channel through which wallets transmit address-bearing traffic to external endpoints. Third-Party Domains Receiving Addresses (most contacted) 4.3.2 Cross-Dataset Summary of Third-Party Connectivity. 1st etherscan.io (9) etherscan.io (7) infura.io (5) We applied the improved framework across Torres-2023/100, Torres- 2nd infura.io (9) infura.io (6) aptoslabs.com (4) 3rd binance.org (4) avax.network (5) sentry.io (3) 2025/100, and CWS-10K/85. While the first two datasets enable a 4th sentry.io (3) binance.org (4) publicnode.com (3) time-separated comparison on the same set of extensions, CWS- 5th rabby.io (2) sentry.io (3) arbitrum.io (3) 10K/85 provides a broader and more recent snapshot of today’s browser-wallet ecosystem. After excluding broken and some par- Table 1: Comparison of wallet address leakage and tially functional extensions, 42, 43, and 57 wallets respectively pro- third-party connectivity across the Torres-2023/100, Torres- duced analyzable address-bearing traffic. 2025/100, and CWS-10K/85 datasets. We no longer attempt to filter vendor-operated domains from other third-party domains, since both are external to the user. Ta- ble 1 categorizes the wallet address leakage and third-party con- • Address Co-Occurrence: Two or more addresses appear nectivity across these three datasets. together in the same request (e.g. batched balance queries). Across all datasets, address leakage to RPC endpoints is com- This provides a definitive linkability signal that the ad- mon, while transmissions to analytics or telemetry services are dresses originate from the same wallet instance. comparatively rare. The modern ecosystem is highly fragmented: • Address Timing Correlation: Requests containing differ- in CWS-10K/85, nearly 90% of domains receiving address-bearing ent addresses are sent within a short time window. This requests are contacted by only a single wallet. This indicates a provides only a heuristic signal: closely timed lookups may shift away from shared, easily identifiable RPC providers (like suggest that the addresses are managed by the same wallet infura.io and etherscan.io) toward wallet-specific backend do- instance, but this inference is less reliable and becomes more mains. Many wallets proxy their RPC requests through proprietary informative when combined with other metadata (e.g., IP vendor-operated domains, which obscures the identity of the under- address). lying node provider while centralizing visibility of users’ address queries within the wallet vendor itself. An external endpoint observing either of these patterns can infer structural relationships between a user’s addresses, even without 4.3.3 Address Correlation in Multi-Account Wallets (CWS- user interaction or webpage involvement. 10K/85). We next evaluated whether outbound RPC traffic reveals relationships between multiple accounts within the same wallet. Among the 57 analyzable wallets in CWS-10K/85, 55 allowed the 4.3 Network-Side Results creation of at least three working test accounts. We applied the improved request-interceptor framework to all three We consider two correlation indicators defined in Section 4.2: wallet datasets and analyzed the address-bearing traffic emitted dur- (i) multiple addresses co-occur within the same request, and (ii) ing measurement procedure. Our analysis quantifies (i) the preva- requests containing different addresses showing timing correlation. lence of address exposure to external endpoints and (ii) the extent Across the 55 multi-account wallets, 13 leaked two or more test to which these requests reveal structural relationships between addresses in the same request to at least one endpoint, and 11 ex- multiple addresses within the same wallet. hibited timing correlation (within 10ms time window) between requests containing different addresses. In total, 17 wallets ex- 4.3.1 Improved Coverage of Address Exposure in Legacy posed at least one of these correlation signals. An estimated Datasets. We capture address-bearing traffic from Torres-2023/100 22.1 million users (62.9%) of 35.16 million users in CWS-10K/85 using our improved network interceptor framework. Torres et al. 3 Hand-curated domain list used by Torres et al. to filter vendor-operated endpoints in reported address leakage only to non-vendor-operated domains, their public analysis code: https://github.com/christoftorres/Web3-Privacy/blob/main/ filtering out vendor-operated endpoints using a hand-curated list of wallet-address-leakage/analysis/find-leaks-and-scripts-wallet-extensions.py#L228 528 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) from the same wallet instance, while timing correlation provides a Co ccu na ent d m ion -o o A ipi de -o ren ly s ur e s cc c tic Co r. t Rec bed Do lat weaker but still informative indicator of such relationships. . om e . d . m in rr .D We also observe a shift toward wallet-specific backend domains. Ad dr s e m Co Ad ic Ti ng g # lyt This centralizes visibility within individual vendors while increas- i m a An Wallet Users ing the number of parties that receive address-bearing traffic. Ti MetaMask ◦ 3 ◦ • metamask.io ◦ 14M In practice, users have little control over which entities learn Phantom ◦ 1 ◦ • phantom.app ◦ 5M their network activity. These findings show that users implicitly OKX • 1 ◦ ◦ – ◦ – 2M entrust wallet vendors and the external services the vendors rely Ronin • 3 ◦ ◦ – ◦ – 1M on with sensitive address-level information. For actively malicious Coinbase • 2 ◦ • coinbase.com • cbhq.net 1M (or compromised) vendors, such visibility could enable targeted coinbase.com spear-phishing campaigns against high-value users [11, 16]. Trust • 1 ◦ ◦ – ◦ – 1M Keplr • 6 ◦ ◦ – ◦ – 1M 5 Web-Side Threats and Results Rabby • 1 ◦ ◦ – ◦ – 900K Solflare ◦ 1 ◦ • solflare.com • solflare.com 800K 5.1 Threat Model Backpack • 1 ◦ ◦ – • xnfts.dev 600K The adversary is any third-party tracker script intentionally in- TronLink • 2 • • tronlink.org • tronlink.org 600K cluded by an otherwise benign webpage, for example for analytics, Bitget ◦ 1 ◦ ◦ – ◦ – 400K performance monitoring, telemetry, or user-experience features. Petra Aptos • 3 ◦ ◦ – ◦ – 400K Station • 2 • ◦ – ◦ – 300K Once loaded, such scripts execute with the same origin privileges Ready • 1 ◦ ◦ – ◦ – 300K as the embedding webpage and can access wallet provider objects Xverse ◦ 1 ◦ ◦ – ◦ – 300K exposed to the webpage via EIP-6963. As a result, they can observe: Martian • 3 • • mixpanel.com • aptoslabs.com 200K • the presence of installed wallets through EIP-6963 discov- mixpanel.com ery events, for example, eip6963:announceProvider and Leap • 4 ◦ ◦ – ◦ – 200K eip6963:requestProvider SubWallet ◦ 15 ◦ ◦ – • alchemy.com 200K • the return value of the restricted method eth_accounts, avail.so which may silently reveal addresses previously authorized blockscout.com publicnode.com for the webpage origin, since third-party scripts embedded subscan.io in the page execute under that same origin zora.energy The adversary executes arbitrary JavaScript in accordance with Suiet ◦ 1 ◦ ◦ – ◦ – 200K browser semantics. It cannot bypass the Same-Origin Policy (SOP). Total • 13 3 6 6 The adversary can access all currently available wallet provider methods. Restricted methods such as eth_accounts only yield ad- • indicates the presence of the corresponding behavior, while ◦ indicates its absence. dresses if the user previously granted permission to the webpage Table 2: Linkability indicators for the 20 most installed wal- origin and that permission has not been revoked. The adversary pas- lets in CWS-10K/85 dataset, covering analytics use, third- sively inspects these responses but does not alter wallet behavior. party recipients of wallet addresses, address leaks to analyt- It cannot approve wallet prompts, and cannot extract private keys ics sites, co-occurrence and timing signals, and user counts. or authorize restricted operations without explicit user interaction. We also do not assume access to persistent browser storage (e.g., cookies or localStorage), representing users who routinely clear are affected by co-occurrence and 23.0 million users (65.4%) are such state or employ privacy-preserving browser settings. affected by at least one of the two signals. We assume the dApp tries to revoke the permission to the wallet Table 2 shows these behaviors for the twenty most widely in- from their side properly by using the wallet_revokePermissions stalled wallets in CWS-10K/85. The table reports whether any an- method. alytics site is embedded, the number of distinct domains that re- ceive address-bearing requests, whether any of these domains are 5.2 Threat#1: Wallet-Based Fingerprinting via analytics services, and the observed linkability signals, including EIP-6963 Discovery address co-occurrence, timing correlation, and the specific domains Adversary: A third-party tracker script embedded on any websites to which these signals were leaked. (not limited to dApps). Source of Leakage: EIP-6963 provider discovery events. 4.4 Discussion EIP-6963 enables websites to request a response from all the in- These results show that network-side privacy exposures stem di- stalled wallets by dispatching the eip6963:requestProvider event rectly from routine wallet behavior. Because wallets automatically on the window. Each EVM-compatible wallet responds with an issue address-bearing RPC requests in the background, external eip6963:announceProvider event containing its name and provider endpoints gain visibility into users’ addresses and, for many wallets, metadata. This allows a third-party tracker script on any website the relationships between multiple addresses. In particular, address to learn: co-occurrence directly reveals that multiple addresses originate • which wallets the user has installed, 529 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. Figure 2: Single-site cross-session re-identification and ad- Figure 3: Cross-site cross-session tracking and wallet-address dress clustering via stale addresses returned by revocation- clustering enabled by stale permissions and shared third- unsafe wallets. party trackers. • how many wallets are present, (3) Session 3: The user revisits the dApp without any action. • the exact combinations of wallets, which forms a stable and The tracker still receives 𝐴2 from 𝑊𝑞 via eth_accounts. potentially distinguishing fingerprint. (4) Session 4: The user revisits the dApp, connects wallet 𝑊𝑝 Wallet-installation patterns are more distinctive than common and grants a fresh address 𝐴3 . The stale 𝐴2 continues to browser fingerprints (fonts, canvas, etc.) and typically change slowly. appear. Industry reports also indicate that many cryptocurrency users man- The tracker can therefore conclude: age more than one wallet [7, 8], suggesting a greater diversity of • The same user visited in sessions 2, 3, and 4, possible installed-wallet combinations. Because discovery requires • Addresses 𝐴2 and 𝐴3 belong to the same user. no user interaction, this fingerprinting attack applies to: Because blockchain addresses are globally unique and cannot • users who never connected a wallet to the site, be produced in a wallet without owning the private key, the stale • users who block cookies or clear browser storage. entry functions as a very strong and more durable identifier, As a result, EIP-6963 provides a new browser-level fingerprinting even if the user rotates wallets or switches accounts. Unlike cookies vector targeting at the Web3 wallet users. or localStorage values, 𝐴2 is stored in extension-controlled storage and cannot be cleared, overwritten, or spoofed. The only mitigation 5.3 Threat#2: Cross-Session Tracking and available now is for the user to manually clean up the permissions Addresses Clustering inside the wallet’s “Connected Sites” menu. Adversary: A third-party tracker script embedded on a dApp Hence, these stale entries persist across page reloads, browser Source of Leakage: The lack of a standardized dApp-side permis- restarts, and even after the user clear their browser cache. sion revocation mechanism. 5.4 Threat#3: Cross-Site Tracking and EIP-2255 does not define any expiration, renewal, or time-based Addresses Clustering across dApps invalidation of permissions, and there is no revocation standard. Trackers embedded on a dApp can see the granted addresses of the Adversary: A shared third-party tracker script embedded on mul- dApp by calling eth_accounts without user interaction provided tiple dApps. that the wallet has not revoked the dApp’s permission to access its Source of Leakage: The lack of a standardized dApp-side permis- addresses. sion revocation mechanism. We call a wallet revocation-unsafe if the wallet continues re- Cross-site tracking arises when multiple dApps share the same turning previously authorized addresses through eth_accounts third-party tracker. With first-party privileges on each site, the after receiving a revocation request wallet_revokePermissions script can detect all the installed wallets, and invoke eth_accounts from a dApp. independently on every dApp where it appears. Figure 2 shows cross-session re-identification and addresses clus- If the user has at least one revocation-unsafe wallet, the stale tering. Suppose the user has at least one revocation-unsafe wallet: address returned by that wallet becomes visible to the shared tracker on that site. Figure 3 illustrates how this results in cross-site tracking (1) Session 1: The user connects with address 𝐴1 . The wallet 𝑊𝑝 and multi-address clustering. correctly revokes this permission when the user disconnects via the dApp UI (green border). 5.4.1 Tracking. Suppose the user previously granted address 𝐴1 (2) Session 2: The user revisits the dApp, connects a differ- to dApp 𝐷𝑥 using a revocation-unsafe wallet. Even if the user later ent wallet 𝑊𝑞 and grants 𝐴2 , but 𝑊𝑞 does not remove the switches wallets or accounts, the stale entry 𝐴1 continues to appear site’s permission when the dApp requests a disconnect (red through eth_accounts, allowing sessions 2 and 3 on 𝐷𝑥 to be linked border). to the same user. The same occurs independently on dApp 𝐷 𝑦 . 530 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) If a third-party tracker 𝐺 is embedded in both 𝐷𝑥 and 𝐷 𝑦 : on Site 𝐷𝑥 , 𝐺 sees the stale address 𝐴1 , and on Site 𝐷 𝑦 , 𝐺 also sees 𝐴1 . Therefore, the tracker can immediately infer that the user visiting 𝐷𝑥 and 𝐷 𝑦 is the same individual. 5.4.2 Wallet Clustering. As we discussed in Threat 5.3, all sub- sequent sessions on 𝐷𝑥 and 𝐷 𝑦 remain linkable. On 𝐷𝑥 , the tracker observes addresses {𝐴1, 𝐴2, 𝐴3 } across sessions. On 𝐷 𝑦 , the tracker separately observes {𝐴1, 𝐴4, 𝐴5 }. Because both sets contain the same stale identifier 𝐴1 , the tracker can merge them into a single cluster: {𝐴1, 𝐴2, 𝐴3, 𝐴4, 𝐴5 }. A similar process occurs on Site 𝐷𝑧 , where a different stale iden- tifier 𝐴7 creates a separate cluster {𝐴7, 𝐴8 }. These two clusters remain disjoint until any address appears in both. In the example of Figure 3, the appearance of 𝐴5 on 𝐷𝑧 links 𝐷 𝑦 and 𝐷𝑧 , enabling Figure 4: A shared third-party tracker on websiteA.com em- the tracker to conclude: beds an invisible iframe of dappX.com. If the wallet exposes • Sites 𝐷𝑥 , 𝐷 𝑦 , and 𝐷𝑧 were visited by the same user. its provider to cross-origin iframes, the tracker inside the • The combined address set {𝐴1, 𝐴2, 𝐴3, 𝐴4, 𝐴5, 𝐴7, 𝐴8 } belong iframe can read the user’s previously authorized address and to that user. pass it back to the tracker on websiteA.com. This cross-site clustering extends the leakage beyond a single The observed address can then be passed from the tracker 𝑇 origin. While Threat#2 in Section 5.3 links sessions within one inside the iframe to the tracker 𝑇 on websiteA.com, allowing it to dApp, a shared tracker aggregates stale identifiers across every identify the user and link the address to the user’s activity on that dApp that embeds it. As a result, a single revocation-unsafe site. wallet enables third-party domains to build ecosystem-wide The tracker does not need to know in advance which dApp, if profiles, merging wallet addresses and activity patterns observed any, the user has previously connected. It can embed one or more on multiple unrelated sites. The more widely a tracker is embedded, candidate dApps that also include the same tracker and test them the larger the portion of the user’s Web3 activity it can reconstruct. opportunistically. The attack succeeds for any embedded dApp to which the user previously granted wallet access and for which the 5.5 Threat#4: Tracking and Deanonymization wallet exposes its provider inside the iframe. beyond dApps 5.5.1 Cross-Session Tracking on Any Website. Once extracted, Adversary: A third-party tracker script shared between a website the information of the address can be used as a stable, cross-session and a previously connected dApp. identifier on any website. Because wallet addresses are globally Source of Leakage: The combination of (i) wallet provider expo- unique, and the permission persists if the user never revokes it, sure in cross-origin iframes, (ii) dApps that permit iframe embed- the tracker gains a unique and long-lived identifier for the user, ding. enabling cross-session tracking on that website. Whereas Threat#3 requires that a user at least once grant the 5.5.2 Linking Web Activities to Web3 Identities and On- same address to different dApps for a tracker to link two address Chain Wealth. The exposed wallet address serves as a persistent clusters (see Figure 3, Sites 𝐷 𝑦 and 𝐷𝑧 ), we now present a more identifier across different websites that embed the same tracker. As general attack that does not require this assumption. This attack is a result, the tracker can link a user’s activity across sites. Combined also applicable to any website, not just dApps. with the address clustering described in Threat 5.4, this allows Assume that address 𝐴1 has previously been granted by the the tracker to associate diverse Web2 activities, including news wallet to dappX.com. A tracker running on websiteA.com can not consumption, shopping behavior, and search queries, with the same access this information, because the tracker 𝑇 is confined to the cluster of Web3 addresses revealing the user’s on-chain wealth. origin of the site it runs on, and wallets strictly validate the origin of any incoming request. 5.5.3 Deanonymization of Web3 Identities. If the website ex- However, as seen in Figure 4, tracker 𝑇 on websiteA.com can poses any real-world user attributes in the DOM (e.g., email address, embed one (or more) invisible iframes in order to load iframe- display name, phone number, or identifiers associated with Google embeddable dApps which also include 𝑇 . or Facebook logins), these become visible to the tracker’s JavaScript. For wallets that expose their provider objects to cross-origin The tracker can therefore link: iframes and do not restrict provider access to the top-level browsing • Web2 identity: user information exposed by the site, context, the instance of 𝑇 executing inside such an iframe runs as a • Web3 identity: the user’s wallet address obtained by the same-origin script on the embedded dApp’s origin and can invoke injected iframe, and the address clusters from Threat 5.4. eth_accounts. If the user has previously granted wallet access to A single popular dApp can be sufficient for this attack. Once that dApp, the address becomes visible to the tracker inside the the tracker is able to extract a wallet address through an iframe- iframe. embeddable dApp for which the user has previously granted access, 531 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. Table 3: Revocation behavior among the 20 most widely Behavior Count Percentage used EVM-compatible browser-extension wallets (≥ 100,000 Do not invoke wallet_revokePermissions 19 (19/30) 63.3% Chrome Web Store users). Calls eth_accounts before permission 18 (18/30) 60.0% Stores address in localStorage/cookies 27 (27/30) 90.0% Wallet Revocation unsafe Error returned? Users Do not clear stored address on logout (of 27) 17 (17/27) 63.0% Contacts ≥1 third-party tracker 19 (19/30) 63.3% MetaMask ◦ – 14M Contacts ≥3 third-party trackers 14 (14/30) 46.7% Phantom • Not supported 5M OKX Wallet • – 2M Ronin Wallet • Not supported 1M Table 4: Summary of permission- and tracking-related be- Coinbase Wallet • Not supported 1M haviors observed across 30 popular Ethereum dApps. Trust Wallet • – 1M Keplr ◦ – 1M Revocation Support. Of these discoverable 36 wallets, 22 (61.1%) Rabby Wallet ◦ – 900K did not correctly implement permission revocation. Of these, 15 Backpack • Not supported 600K explicitly returned an error indicating that the revocation method Bitget Wallet • Not supported 400K was unsupported (e.g., “wallet_revokePermissions does not exist/is not Ctrl Wallet ◦ – 300K available”). Such errors are surfaced to the dApp but not displayed Bybit Wallet • Not supported 200K to the user. The remaining 14 wallets successfully removed the Leap Wallet ◦ – 200K permission entry associated with the testing origin. SubWallet ◦ – 200K Table 3 summarizes revocation behavior for the 20 most widely Gate Wallet • Not supported 100K Zerion Wallet • Not supported 100K installed EVM-compatible wallets (≥100,000 Chrome users). A com- Pontem • Not supported 100K plete list of all 36 discoverable wallets is provided later in Table 5. Coin98 • – 100K Post-Revocation Behavior. All 22 wallets that failed to revoke Portal DEX • – 100K permissions continued to return the previously granted address Exodus Web3 Wallet ◦ – 100K when queried with eth_accounts, even after a new session. This behavior also persisted sometimes when the wallet UI was explicitly “Revocation unsafe” indicates whether invoking wallet_revokePermissions removed the origin’s permission entry from the wallet’s internal state (• = permission locked. This demonstrates that these wallets retain stale permission persisted; ◦ = permission successfully cleared, such that subsequent eth_accounts state internally and continue to expose user addresses to the same calls returned no addresses) origin despite receiving a revocation request. “Error returned?” indicates whether the wallet returned an explicit error in response to the revocation request (e.g., “method not supported”). “–” denotes that the wallet returned no error message, regardless of whether revocation succeeded. 5.6.3 dApp Permission and Tracking Behavior. We analyzed 30 popular Ethereum dApps from DappRadar’s Ethereum category to observe how real sites handle wallet permissions and user dis- any website embedding the same tracker can contribute additional connection (see Table 4). Web2 or Web3 identity signals. As the tracker appears across more Invocation of Permission Revocation. Only 11 out of 30 dApps websites, it can reconstruct an increasingly complete view of the (36.7%) invoked a wallet_revokePermissions method when the user’s combined Web2 and Web3 activity. user clicked a “Disconnect,” “Logout,” or similar UI control on the site. The remaining 19 dApps performed the disconnect action only 5.6 Web-Side Results at the application level: they cleared their own interface state but 5.6.1 EIP-6963 Discovery Support. Of the 85 wallets in CWS- never issued a revocation request to the wallet provider. 10K/85, 36 exposed an EVM-compatible provider interface and could Probe Accounts Before Explicit Permission. 18 of the 30 dApps be detected without unlocking by EIP-6963 events. Importantly, (60%) called the restricted method “eth_accounts” before requesting despite representing only 42% of the wallets in the dataset, these any permission-granting API. Wallets are required to return an 36 EVM-compatible wallets collectively have 29.08 million Chrome empty array when no permission has been granted, but any wallet Web Store users, which is 82% of the total 35.16 million users with stale permission state will still return the previously authorized represented in CWS-10K/85. This indicates that our selection addresses. This means pre-permission probes can reveal a user’s captures the majority of the user base in the dataset. address if the wallet does not handle revocation correctly. 5.6.2 Wallet Permission Revocation Behavior. We evaluated Client-Side Storage of Wallet Addresses. Our framework mon- how wallets in CWS-10K/85 handle permission revocation and itored changes to browser storage during the workflow. 27 of the whether a dApp can still access previously granted addresses after 30 dApps (90%) stored the connected wallet address in browser- a disconnect action. side storage, either localStorage or cookies, at some point during the session. These identifiers survive page reloads and enable re- Analysis Scope. These 36 wallets all exposed an EIP-6963 discov- identification within the same site. 17 of these 27 dApps did not ery interface, allowing programmatic interaction through standard clear the stored address upon logout. provider APIs. They constitute all EVM-compatible wallets in the dataset; non-EVM wallets did not expose a compatible provider and Presence of Third-Party Analytics and Trackers. Outbound were excluded from further analysis. request logs show that 19 out of 30 dApps (63.3%) contacted at least 532 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) d d • Iframe Exposure (23/36): whether the wallet injects its ns ocke n s o ck e e e provider into an embedded iframe of a dApp and do not Re s Wh osur Re s Wh osur c. U en L c. U en L afe afe restrict access. This determines whether an attacker can xp xp access the wallet provider from within the dApp iframe. Le e E Le e E • Leaks When Locked (14/36): if calling eth_accounts from am am vo vo ak ak Ifr Ifr Wallet Users Wallet Users within that iframe returns an address even when the wallet is locked. This affects whether cross-browser-session iden- MetaMask • • ◦ 14M Exodus ◦ – ◦ 100K Phantom • • • 5M StarKey ◦ – ◦ 100K tification is possible when the wallet auto-locks when the OKX • • • 2M Rainbow ◦ – ◦ 100K browser is closed. Ronin • ◦ • 1M TokenPocket ◦ – • 90K • Revocation Unsafe (22/36): whether the wallet continues Keplr • ◦ ◦ 1M Binance • • ◦ 70K to expose previously granted addresses after a dApp requests Trust • • • 1M Core • ◦ • 60K permission revocation, which is derived from the revocation Coinbase • • • 1M MathWallet • • • 50K experiment. Rabby • ◦ ◦ 900K Enkrypt ◦ – • 50K Backpack • • • 600K QSafe ◦ – • 30K 5.6.5 Feasibility and Impact of Threat #4. The measurements Bitget ◦ – • 400K OneKey • • ◦ 30K show that the components required for iframe-based cross-site Ctrl ◦ – ◦ 300K Wigwam • ◦ • 20K wallet tracking are widely present in the current ecosystem. On the Bybit • ◦ • 200K Fin • • • 20K dApp side, 18 of the 30 Ethereum dApps we analyzed are iframe- Leap • ◦ ◦ 200K Fluvi ◦ – ◦ 20K embeddable, meaning a malicious site can load them invisibly in SubWallet • • ◦ 200K Hana • ◦ • 10K a cross-origin iframe. Among these 18, 11 perform no permission- Zerion • ◦ • 100K Stargazer ◦ – • 10K Coin98 • • • 100K Flow ◦ – ◦ 10K revocation at all, so any address the user previously granted to Gate • • • 100K Koala ◦ – ◦ 10K these dApps remains readable to scripts executing inside the iframe Pontem • • • 100K no matter if user clicks “disconnect” or not. Total • 23 14 22 29.08M Portal DEX ◦ – • 100K • indicates the presence of the behavior, while ◦ indicates its absence. Table 5: Per-wallet iframe exposure, locked-state leakage, and revocation behavior (split into two columns). one third-party analytics or telemetry service during the workflow, and 14 of those contacted three or more distinct tracking domains. The most common destinations were: • Google Analytics / Google Tag Manager (13 dApps) • Sentry (8 dApps) • Intercom (4 dApps) These findings show that many dApps incorporate third-party Figure 5: Outcome tree showing which wallets (referenced in analytics or telemetry services as part of their client-side operation. Table 5) and what share of CWS-10K/85 users remain vulner- able under different disconnect, revocation, and locked-state 5.6.4 Iframe Exposure of Wallets and dApps. Threat #4 (Sec- conditions. tion 5.5) requires both (i) a wallet that exposes its provider inside a cross-origin iframe and does not restrict provider access to the On the wallet side, 23 of the 36 discoverable EVM-compatible top-level browsing context, and (ii) a dApp whose frontend can be wallets expose their provider interface into embedded iframes, cov- embedded as an iframe. Therefore, we measured these two dimen- ering 27.76 million users (78.95% of the entire CWS-10K/85 dataset). sions for all wallets and dApps in our dataset CWS-10K/85. Any such wallet automatically hands its provider to whatever dApp the malicious site embeds, without user interaction or visibility. dApps Iframe Embeddability. For Threat#4, a malicious site Figure 5 shows that almost all realistic user workflows expose the must embed a real dApp inside an invisible iframe. Across the 30 user’s address to third-party trackers. If the user never disconnects Ethereum dApps we analyzed, 18 were fully iframe-embeddable, from the dApp (or can’t), and the wallet is unlocked, all these including several widely used platforms such as Uniswap, Aave, 23 wallets leak the user’s active address immediately. When Lido, and PancakeSwap. Only 12 dApps set framing protections users do disconnect, in many cases, the problem persists. Among (e.g., X-Frame-Options: DENY or CSP frame-ancestors) that pre- these 23 iframe-exposing wallets: vent their frontend from being loaded inside a cross-origin iframe. • 16 are revocation-unsafe: even if the user wants to discon- Iframe-embeddable dApps give an attacker a usable execution en- nect from the dApp side, the user is unable to. vironment where an embedded tracker script can access a wallet • 14 leaks the address even when locked: 69% of users are provider that exposes itself inside the iframe. still under threat even when the wallet is locked. Wallet Iframe Exposure and Locked-State Leakage. Table 5 In practice, for a very large portion of users, locking does not summarizes three behaviors relevant to Threat #4 (Section 5.5): protect them, disconnecting does not protect them, and wallet 533 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. Threat Cause # Wallets Estimated Users Network-Side Threat (Adversary: external service endpoints) #1 Address linkability Address batching or short-interval network requests 17 / 85 (20%) ∼23.0M (65.4%) Web-Side Threats (Adversary: third-party trackers) #1 Wallet-based fingerprinting EIP-6963 wallet discovery reveals installed wallet combinations 36 / 85 (42.4%) ∼29.08M (82%) #2 Cross-session tracking & address clustering Stale address persistence after wallet_revokePermissions call 22 / 36 (61.1%) ∼12.04M (34.2%) #3 Cross-dApp tracking & address clustering Stale address persistence after wallet_revokePermissions call 22 / 36 (61.1%) ∼12.04M (34.2%) #4 Cross-any-site tracking Wallet provider exposure on cross-origin contexts 23 / 36 (63.9%) ∼27.76M (78.95%) Table 6: Summary of the five privacy threats identified in browser-extension wallets, their causes, affected wallet numbers and ecosystem impact. Wallet counts and user counts are based on the CWS-10K/85 dataset. For web-side threats #2–#4, percentages of affected wallets are computed over the 36 wallets responding to EIP-6963 events in web-side threat #1, while user counts are computed over the full dataset. revocation is simply not implemented. For millions of users, wallet We therefore propose three mitigations: address leakage is just the default outcome. (1) Ecosystem-wide revocation semantics. Wallet address permission revocation should be defined and implemented by both 5.7 Discussion wallets and dApps. Web-side linkability arises from inconsistent permission handling, (2) Permission expiry: Wallets should limit the lifetime of iframe exposure, and widespread third-party scripts across wallets address permissions to avoid the existence of long-lived stale per- and dApps, enabling passive address recovery across sessions and missions. Brave Wallet already adopts this approach. sites even when users believe they have disconnected or locked (3) Restrict repeated account access: Wallets should not allow their wallet. Taken together, the results show that these leaks are dApps to repeatedly query address information without additional not isolated bugs but systemic interactions across wallets, dApps, user interaction. Subsequent queries should require explicit consent ecosystem standards, and embedded scripts. Because the permission from the user, preventing continuous passive access by the dApp. model is inconsistently enforced, and because iframe exposure by- However, these measures still do not eliminate the tracking risk passes traditional Web2 tracking defenses, a determined tracker during the time window in which a permission remains valid, al- can link user activity across the web and even connect wal- lowing a tracker embedded in the web page to still access it. let addresses to a user’s real-world identity despite careful To address it, we propose a newly designed script-level access- cookie or storage hygiene. controlled localStorage for wallet permissions, similar to prior work on per-script-domain cookie isolation [25]. Current localStor- 6 Summary and Mitigation age is bound only to the page origin, meaning that third-party scripts embedded in the web page share the same page origin and Table 6 summarizes the five privacy threats we identified in browser- can access the same data. Our design adds a check if the origin extension wallets, their causes, and their ecosystem impact. We of the calling script matches the origin of the web page, thereby now outline several mitigations that can reduce these privacy risks. preventing embedded third-party scripts from accessing it. In this Network-Threat#1. Wallets should avoid batching multiple design, the wallet stores its per-origin permissions in script-level user addresses into a single RPC request, as this creates strong access-controlled localStorage rather than in extension-controlled address co-occurrence linkability signals without providing func- storage, so that only first-party page scripts can access the associ- tional benefits beyond developer convenience. Each RPC request ated addresses. An additional benefit is that permissions stored in should contain only one address to prevent direct linkage. Addi- localStorage are automatically cleared when users clear site data. Al- tionally, timing obfuscation (e.g., randomized delays or lightweight though browsers do not currently provide such script-level storage mixing) can be applied on the user side to reduce time-correlation isolation natively, wallet extensions can approximate this design linkability. today by performing the same script-origin check based on the JavaScript Stack before returning addresses. Web-Threat#1. One possible way to prevent fingerprinting is to block EIP-6963 discovery events. However, wallet extensions may inject page scripts and dispatch these events before any user-side Web-Threat #4. This threat arises from wallet providers being mechanism can intervene, making this defense unreliable. A more injected into cross-origin contexts. The only reliable mitigation is effective strategy would be for wallets to only enable announce to restrict provider exposure. messages when the wallet is unlocked. This allows dApps to detect Wallets should therefore inject providers only into top-level, wallets only when the user chooses to do so, while preventing same-origin contexts. In addition, dApps should enforce standard unsolicited exposure of the user’s installed-wallet set. framing protections (e.g., frame-ancestors or X-Frame-Options) to Web-Threats #2–#3. These threats originate from long-lived prevent malicious embedding. stale permissions stored by wallet extensions. We observed that this Alternatively, wallets may continue injecting providers into is not solely a wallet-side problem, but an ecosystem-wide issue, as cross-origin contexts but enforce strict origin verification most dApps also fail to revoke permissions properly. before serving requests. Specifically, the wallet verifies that the 534 Privacy Threats of Browser-extension Wallets in the Web3 Ecosystem Proceedings on Privacy Enhancing Technologies 2026(3) origin of the calling script matches the top-level page origin before Yet, on the network side, wallets often batch or structure network re- returning any wallet data. quests in ways that reveal relationships between a user’s addresses. On the web side, wallet discovery APIs, the lack of ecosystem-wide revocation mechanisms, and cross-origin provider injection expose 7 Related Work information about users and their addresses in ways that users may not expect. Prior research has extensively examined web-based device finger- As a result, these behaviors enable external adversaries to infer printing and browser-exposed identifiers [15, 24, 26, 31]. Work such multi-address ownership, fingerprint Web3 wallet users, enable as Carnus [20] shows that browser extensions leak fingerprintable persistent user tracking across sessions and sites, and ultimately artifacts, while systems like CloakX [30] and Simulacrum [21] at- link users’ web activity to their on-chain wealth. tempt to mask extension-induced signals. Agarwal et al. [1] further We discuss several mitigations for these threats. Addressing them show that extension code injection and event-driven behaviors are will require more privacy-preserving handling of wallet-related net- observable from the page. Our work focuses specifically on Web3 work requests, stronger privacy considerations in ecosystem stan- wallet extensions and highlights how emerging wallet standards dards for wallet discovery and permission revocation, and stricter introduce new, Web3-native fingerprinting vectors. controls over cross-origin provider exposure to place user privacy A separate line of work studies off-chain network-layer or on- at the core of Web3 wallet design. chain metadata leakage. Users can be deanonymized via P2P traffic patterns [4, 5, 17], RPC timing correlations [34, 35], centralized RPC infrastructure [38], and on-chain graph analysis [2, 3, 6, 19, 22, 28, 9 Open Source and Demo 32]. These approaches focus on blockchain-level or network-level Our frameworks, datasets, and analysis code are released as open signals rather than the wallet extension, which is often the user’s source4 , and we provide a public demo that allows anyone to easily first point of contact with Web3. test the web-side threats of wallet extensions.5 Within the browser-extension wallet ecosystem, prior work has mostly examined their security. Houy et al. [18] and recent SoKs [10] systematize wallet architectures and high-level attack 10 Responsible Disclosure surfaces. WalletRadar [37] performs large-scale analysis to un- We focused our disclosure efforts on web-side threat #4, which cover code-level vulnerabilities but does not study privacy leakage does not stem from ecosystem standards and can be addressed through web- or network-side behaviors. Our work fills this gap. directly by wallet developers. The other threats primarily arise Closest to our study are Torres et al. [29] and Winter et al. [36]. from ecosystem-level design decisions or wallet implementation Torres et al. [29] measure the endpoints contacted by wallets but choices. treat all requests uniformly. In practice, many of these requests In February 2026, we retested the affected wallets using the are functional RPC calls; we instead analyze the privacy impli- latest versions available on the Chrome Web Store with our web cations of multi-address exposure within these RPC flows, exposure demo5 . Out of the 23 wallets originally affected by threat which their endpoint-level analysis does not capture. Winter et #4, two wallets (Coinbase Wallet v3.120.0 and Coin98 v10.4.1) were al. [36] show that DeFi frontends embed third-party trackers and no longer vulnerable in their latest versions. We therefore contacted frequently leak wallet addresses to analytics providers, enabling the vendors of the remaining 21 wallets. cross-site and Personally Identifiable Information (PII) linkage. Our Within a one-month notification window prior to the camera- results reveal a related but distinct problem: a tracker can learn ready submission, eight wallets responded to our reports through a user’s address without any action from the dApp, because wal- their bug bounty programs, including MetaMask, OKX, Trust, Rabby, lets themselves passively disclose addresses. This issue enables Backpack, Bybit, Zerion, and Core. Most vendors simply classified cross-site tracking, account clustering, and deanonymization Prior the issue as informational or out of scope for their bug bounty work has mostly reported on dApp leaks or network metadata in programs. isolation. Our results show that modern Web3 privacy risks emerge OKX acknowledged the technical correctness of our findings from the interaction between wallets, dApps, third-party end- and the associated privacy implications, but classified the issue as points, and new wallet standards, revealing an ecosystem-level informational because it lacks demonstrable functional or financial attack surface not previously characterized. harm beyond information disclosure. MetaMask confirmed that cross-origin provider exposure is a known risk internally and was one of the main motivations behind 8 Conclusion their development of an alternative wallet API that does not rely on provider injection. They further stated that they currently have We identify five concrete privacy threats of browser-extension no immediate plans to stop injecting the provider, as doing so wallets and quantify their prevalence using measurement frame- would create significant breaking changes for the dApp ecosystem, works that we developed to capture both network-side and web-side although future changes may be considered. traffic. Our findings show that a large majority of active browser- extension wallet users are affected by these threats. In particular, a central cause of these threats is the mismatch between wallet capabilities and their privacy guarantees. Wallets 4 Artifact repository: https://github.com/podiumdesu/wallet-privacy-threats. allow users to manage multiple addresses within a single interface. 5Web exposure demo: https://wallet-privacy.distriled.dnetcloud.cs.kuleuven.be/. 535 Proceedings on Privacy Enhancing Technologies 2026(3) Wang et al. Acknowledgments 1319–1338. 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In Proceedings of the ACM Web Conference 2023 (Austin, TX, USA) (WWW tracking domains used in our classification, grouped by provider ’23). Association for Computing Machinery, New York, NY, USA, 2274–2283. https://doi.org/10.1145/3543507.3583393 category. Category Domain Google Analytics / Ads google-analytics.com googletagmanager.com analytics.google.com g.doubleclick.net stats.g.doubleclick.net doubleclick.net googletagservices.com Product Analytics segment.io amplitude.com mixpanel.com Error / Telemetry sentry.io bugsnag.com newrelic.com datadoghq.com User Engagement intercom.io intercomcdn.com hotjar.com fullstory.com A/B Testing optimizely.com Other Trackers clarity.ms facebook.com B Observed Node Providers and RPC endpoints Wallets query external node providers and RPC endpoints to re- trieve blockchain state (e.g., balances, nonces, and transaction meta- data). These services include commercial node providers, chain- operated infrastructure, and blockchain data APIs. Examples ob- served in our measurements include. Category Domain Commercial Node Providers infura.io ankr.com drpc.org publicnode.com 1rpc.io Chain Infrastructure arbitrum.io avax.network binance.org Blockchain Data APIs etherscan.io aptoslabs.com These domains are representative examples observed in our mea- surements and do not constitute an exhaustive list of infrastructure services contacted by wallets.6 6 A larger community-maintained list of RPC node providers is available at https: //github.com/arddluma/awesome-list-rpc-nodes-providers. 537