How Cloudflare protects customers from cache poisoning

What this post added

This post details how Cloudflare mitigated a practical cache poisoning attack by modifying its cache key logic. The attack exploited origins that reflected data from HTTP headers (not part of the original cache key) into responses. Cloudflare's solution involves including specific 'interesting' headers (X-Forwarded-Host, X-Host, X-Forwarded-Scheme) in the cache key when they differ from the URL or Host header, preventing poisoned responses from being cached and served. The post also mentions proactive customer notification and blocking of malicious requests.