Gitea: Blind SSRF in OAuth2 avatar synchronization via unvalidated OIDC picture claim

Summary When oauth2client UPDATEAVATAR = true is enabled, Gitea fetches the avatar URL received from an OAuth2/OIDC provider using Go's default HTTP client. The URL comes from the user's OAuth/OIDC avatar value, commonly the OIDC picture claim. The affected code path calls http.Geturl without...