Tugtainer: Authenticated SSRF via arbitrary notification URLs in test_notification endpoint

Tugtainer is a self-hosted app for automating updates of Docker containers. Prior to version 1.30.6, Tugtainer allows an authenticated user to make the backend server send outbound HTTP requests to arbitrary user-supplied URLs through the notification test endpoint. The /settings/test_notification endpoint accepts a urls field and passes it directly to Apprise without restricting protocols, hostnames, localhost addresses, private IP ranges, or cloud metadata addresses. This can be abused as an authenticated blind server-side request forgery (SSRF). This issue has been patched in version 1.30.6.