nextcloud-mcp-server: Unauthenticated `POST /webhooks/nextcloud` allows arbitrary vector data deletion when `WEBHOOK_SECRET` is unset ( default )

Summary The POST /webhooks/nextcloud endpoint has no authentication by default: WEBHOOKSECRET defaults to None and is never required by startup validation. When unset, the receiver accepts any unauthenticated POST. The userid is taken directly from the attacker-supplied payload and passed to...