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Why this module exists. James Kettle’s 2018 “Practical Web Cache Poisoning” Black Hat talk made cache poisoning the bug that goes from “weird HTTP behaviour” to “CDN-served XSS to every user in the country.” The bug class hasn’t gone away; if anything it’s gotten worse with the proliferation of CDNs and edge caching.
Why this module exists. James Kettle’s 2018 “Practical Web Cache Poisoning” Black Hat talk made cache poisoning the bug that goes from “weird HTTP behaviour” to “CDN-served XSS to every user in the country.” The bug class hasn’t gone away; if anything it’s gotten worse with the proliferation of CDNs and edge caching.
The mental model
A CDN caches responses. The cache key is normally just { method, URL }. If the response varies based on a header (Host, X-Forwarded-Host, X-Original-URL) that the cache key doesn’t include, an attacker can poison the cache: they make a request that triggers a malicious response, the CDN caches it, every subsequent visitor gets the malicious version.
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