A flaw was found in Red Hat Quay's notification webhook feature. The Slack and generic webhook notification handlers accept user-supplied URLs without SSRF validation, allowing a repository administrator to make the Quay worker issue POST requests to internal network addresses or cloud infrastructure endpoints that should not be reachable from the application.
Restrict network egress from Quay worker pods/containers using network policies or firewall rules to block outbound connections to internal network ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and cloud metadata endpoints (169.254.169.254). Limit repository creation and admin privileges to trusted users. Configure WEBHOOK_HOSTNAME_BLACKLIST in Quay config to include known internal hostnames and IP ranges.