Lab: Web cache poisoning with an unkeyed header
Summary: PortSwigger's lab demonstrates web cache poisoning through an unkeyed header, where the application handles input from that header unsafely. The lab supports the X-Forwarded-Host header, and solving it requires poisoning the cache with a response that executes alert(document.cookie) in the browser of an unsuspecting user who regularly visits the site's home page.
Bottom line: An unkeyed header means one poisoned cached response can be served to every visitor who requests that page, so a single crafted request from an attacker reaches users who never interacted with them.
Read the original at PortSwigger Research ↗
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