Mirror-registry: quay: server-side request forgery in proxy cache upstream registry configuration

A flaw was found in Red Hat Quay's Proxy Cache configuration feature. When an organization administrator configures an upstream registry for proxy caching, Quay makes a network connection to the specified registry hostname without verifying that it points to a legitimate external service. An attacker with organization administrator privileges could supply a crafted hostname to force the Quay server to make requests to internal network services, cloud infrastructure endpoints, or other resources that should not be accessible from the Quay application.