Two endpoints used to preview an MCP server before saving it — POST /mcp-rest/test/connection and POST /mcp-rest/test/tools/list — accepted a full server configuration in the request body, including the command, args, and env fields used by the stdio transport. When called with a stdio configuration, the endpoints attempted to connect, which spawned the supplied command as a subprocess on the proxy host with the privileges of the proxy process.

The endpoints were gated only by a valid proxy API key, with no role check. Any authenticated user — including holders of low-privilege internal-user keys — could therefore run arbitrary commands on the host.

Fixed in 1.83.7. Both test endpoints now require the PROXY ADMIN role, bringing them into line with the save endpoint.

If upgrading is not immediately possible, developers should block POST /mcp-rest/test/connection and POST /mcp-rest/test/tools/list at their reverse proxy or API gateway.