Caddy is an extensible server platform that uses TLS by default. From version 2.10.0 to before version 2.11.2, forward_auth copy_headers does not strip client-supplied headers, allowing identity injection and privilege escalation. This issue has been patched in version 2.11.2.
https://github.com/caddyserver/caddy/security/advisories/GHSA-7r4p-vjf4-gxv4
https://github.com/caddyserver/caddy/pull/7545