Collected research

How to upload arbitrary file contents cross-domain

CORS lets a plain XMLHttpRequest POST cross-domain without preflight, so an attacker page can hand-build a multipart/form-data body and upload a file of chosen name and content to another site with no user interaction. It needs an upload endpoint that does not authenticate, and it exploits a specification quirk rather than a browser bug, so vendors will not patch it.

Record

Published by

blog.kotowicz.net

Topic

Browser

In the archive

• Collected in the 2011 research round
• Collected in the 2012 research round

Related sources

• Cross domain arbitrary file upload Redux
• Cross-domain upload demonstration
• How to upload arbitrary file contents cross-domain

Tags

• csrf
• cors
• file-upload
• javascript
• sop-bypass
• http
• owasp-a01-2021

This page is the archive's own catalogue record. The research is the work of blog.kotowicz.net, first published at the original source. Preserved copies are kept so the citation survives its host; this one was last captured on 10 August 2026.