A Server-Side Request Forgery (SSRF) vulnerability was identified in Red Hat
Quay's repository-level mirror configuration feature. An authenticated
repository administrator can supply an attacker-controlled hostname as the
external_reference parameter when enabling or updating repository mirroring
via endpoints/api/mirror.py (POST and PUT handlers). The value is stored
without SSRF validation and later interpolated into a docker:// URL that
Skopeo uses for HTTP requests, allowing the attacker to force the Quay
mirror worker to connect to internal services.