Forgejo through 15.0.11, 16.0.0 through 16.0.7, and 17.0.0 through 17.0.1 contains a server-side request forgery vulnerability that allows unauthenticated attackers to make the server issue requests by submitting arbitrary OpenID identifier URLs. Attackers can POST crafted identifiers to /user/login/openid to trigger blind discovery GET requests to loopback, cloud metadata, and internal addresses for port scanning and probing.