CVE-2026-33679: Vikjuna Bypasses Webhook SSRF Protections During OpenID Connect Avatar Download

The DownloadImage function in pkg/utils/avatar.go uses a bare http.Client{} with no SSRF protection when downloading user avatar images from the OpenID Connect picture claim URL. An attacker who controls their OIDC profile picture URL can force the Vikunja server to make HTTP GET requests to arbitrary internal or cloud metadata endpoints. This bypasses the SSRF protections that are correctly applied to the webhook system.