parameter-pollution

HTTP parameter pollution (HPP) exploits server-side and client-side parsing inconsistencies by sending duplicate or malformed parameters to bypass access controls, WAFs, and security tokens. Different web servers and frameworks handle parameter precedence differently, creating exploitable flaws.

To test for HPP vulnerabilities, send HTTP requests containing duplicate parameters like `?user=guest&user=admin` to the target URL. This parameter handling analysis reveals if the application server framework interprets the first or last value, exposing access control bypass or data manipulation risks.

Yes, PHP, ASP.NET, and Node.js interpret duplicate HTTP parameters differently. Understanding parameter precedence across these server technologies is essential for discovering HPP vulnerabilities and achieving WAF evasion or access control bypass during vulnerability testing.

HPP can evade WAFs and manipulate server-side data by exploiting parameter parsing inconsistencies. By manipulating duplicate or malformed parameter order and values, attackers bypass security token validation and achieve unauthorized data manipulation on the target web application.

The best way to analyze parameter precedence for HPP vulnerability discovery is testing how various web servers and frameworks process duplicate parameters. Identifying parsing inconsistencies reveals potential access control bypasses and WAF evasion scenarios through malformed parameter manipulation.