CVE-2026-55640 Nextcloud MCP Server: Unauthenticated `POST /webhooks/nextcloud` allows arbitrary vector data deletion when `WEBHOOK_SECRET` is unset ( default )

Nextcloud MCP Server is a production-ready MCP server that connects AI assistants to a Nextcloud instance. Prior to 0.117.2, the POST /webhooks/nextcloud endpoint in nextcloudmcpserver/vector/webhookreceiver.py has no authentication by default because WEBHOOKSECRET defaults to None and startup...