Lab: Parameter cloaking
Summary: PortSwigger's lab demonstrates parameter cloaking against a site vulnerable to web cache poisoning because it excludes a UTM analytics parameter from the cache key, combined with inconsistent parameter parsing between the cache and the back-end. Appending a second callback parameter to utm_content with a semicolon excludes it from the cache key while it still overwrites the callback function in the response, letting an attacker poison the cache with a response that executes alert(1) in a Chrome user's browser.
What's compelling: The gap is a parsing mismatch: the cache and the back-end read the same request differently, so a parameter the cache ignores still reaches the application and changes the response every later visitor receives.
Read the original at PortSwigger Research ↗
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