Michael Winser

The `rebuild.php` front controller, used to clear caches and rebuild the container when a site is in an unexpected condition, fails to correctly validate the Host header against trusted host patterns. This flaw can lead to cache poisoning, where a cache is filled with a malicious response, or an open redirect, which sends users to an attacker-controlled domain.

The Media module supports oEmbed, which utilizes two discovery mechanisms: `providers.json` and URL discovery. The URL discovery code can be exploited to trick the system into making unauthorized server-side requests to any arbitrary URL. This is a Server-Side Request Forgery (SSRF), a flaw where an attacker can force a server to send requests to an unintended location.