Client-side HTTP parameter pollution (reflected)
Summary: Client-side HTTP parameter pollution (HPP) vulnerabilities arise when an application embeds user input in URLs in an unsafe manner, letting an attacker construct a URL that, when visited by another user, inserts additional query string parameters into URLs in the response and sometimes overrides existing ones. PortSwigger notes this can give links and forms unexpected side effects, such as modifying an invitation form so the invitation is delivered to an unexpected recipient.
What's compelling: The impact depends largely on the application's functionality, and even where HPP has no direct impact on its own, an attacker may combine it with other vulnerabilities to escalate overall severity - so a low-severity rating on this finding is not the same as a low-risk one.
Read the original at PortSwigger Research ↗
- Topics
- Vulnerabilities & Patching
- Related
- Attackers Exploit UnrealIRCd Flaw That Enables Server-Level Command Injection Cyber Risks · Nov 14, 2026U.S. CISA adds Check Point and UnrealIRCd flaws to its Known Exploited Vulnerabilities catalog Cyber Risks · Nov 14, 2026PostgreSQL Patches 52 Flaws, Including 22-Year-Old Bug Enabling Authenticated RCE Cyber Risks · Nov 13, 2026