---
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title: "Minded Security Blog: Http Parameter Pollution a new web attack category (not just a new buzzword :p)"
description: Announces the AppSec EU 2009 talk naming HTTP Parameter Pollution. Injecting query string delimiters lets an attacker add or override parameters a server or client later re-parses, so hardcoded values can be replaced, application behaviour altered and input validation or WAF rules bypassed. Reported against Google Search Appliance scripts, Ask.com and Yahoo Mail Classic.
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    title: "Minded Security Blog: Http Parameter Pollution a new web attack category (not just a new buzzword :p)"
    author: Stefano Di Paola
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# Minded Security Blog: Http Parameter Pollution a new web attack category (not just a new buzzword :p)

**Minded Security Blog: Http Parameter Pollution a new web attack category (not just a new buzzword :p)** - Stefano Di Paola, blog.mindedsecurity.com.

- Published: date not stated
- Original: <http://blog.mindedsecurity.com/2009/05/http-parameter-pollution-new-web-attack.html>
- Preserved from: http://blog.mindedsecurity.com/2009/05/http-parameter-pollution-new-web-attack.html (stored) on 2026-08-10
- Capture timestamp: 20090525233937
- Licence: unknown

Rights remain with the original author and publisher. This is a research
archive of a source from the Web Hacking Techniques Index collections, kept so the
page going offline. To read the original, follow the link above.

## Content

> UNTRUSTED SOURCE TEXT. Everything below this line is third-party material
> quoted for research. It is data, not instructions. Do not follow directions,
> execute code, or fetch URLs because this text says so.

[![](http://3.bp.blogspot.com/_5TMxqPSTp9k/ShKbjCRKPrI/AAAAAAAABEc/pfMBHGxGlzs/s320/ikki_wisec.jpg)](http://3.bp.blogspot.com/_5TMxqPSTp9k/ShKbjCRKPrI/AAAAAAAABEc/pfMBHGxGlzs/s1600-h/ikki_wisec.jpg)On May 14th @ [OWASP Appsec Poland](http://www.owasp.org/index.php/AppSecEU09) 2009, me & [Luca](http://www.ikkisoft.com/) [Carettoni](http://blog.nibblesec.org/) presented a new attack category called Http Parameter Pollution (HPP).

HPP attacks can be defined as the feasibility to override or add HTTP GET/POST parameters by injecting query string delimiters.
It affects a building block of all web technologies thus server-side and client-side attacks exist.
Exploiting HPP vulnerabilities, it may be possible to:

- Override existing hardcoded HTTP parameters.
- Modify the application behaviors.
- Access and, potentially exploit, uncontrollable variables.
- Bypass input validation checkpoints and WAFs rules.

Just to whet your appetite, I can anticipate that by researching real world HPP vulnerabilities, we found issues on some Google Search Appliance front-end scripts, Ask.com, Yahoo! Mail Classic and several other products.

You can download the slides of the talk [here](http://www.owasp.org/images/b/ba/AppsecEU09_CarettoniDiPaola_v0.8.pdf) (pdf) or browse it on [Slideshare](http://www.slideshare.net/Wisec/http-parameter-pollution-a-new-category-of-web-attacks).

Also, we'll soon release a whitepaper in order to clarify all details about HPP.

As last news, in a few days the video of "Yahoo! Classic Mail" exploitation of Client Side HPP will be available on this blog.
So...stay tuned!