Termix: Authenticated blind SSRF through notification channel test endpoints

Termix is a web-based server management platform with SSH terminal, tunneling, and file editing capabilities. From 2.5.0 until 2.5.1, Termix allows authenticated users to configure webhook or ntfy notification channels with attacker-controlled destination URLs and trigger server-side requests through the notification-channel test endpoint. The request path in src/backend/database/routes/alert-rules-routes.ts reaches src/backend/utils/notification-sender.ts without destination allowlisting or private-address blocking. This permits blind requests to internal HTTP services reachable by the Termix server. Webhook mode also permits attacker-controlled HTTP methods and headers, which can cause limited state changes when an internal service accepts the fixed notification body, although response bodies are not returned. This issue is fixed in version 2.5.1.