CVE-2025-66454: arcade-mcp-server Has Default Hardcoded Worker Secret That Allows Full Unauthorized Access to All HTTP MCP Worker Endpoints

The arcade-mcp HTTP server uses a hardcoded default worker secret (“dev”) that is never validated or overridden during normal server startup. As a result, any unauthenticated attacker who knows this default key can forge valid JWTs and fully bypass the FastAPI authentication layer. This grants remote access to all worker endpoints—including tool enumeration and tool invocation—without credentials.

Anyone following the official quick-start guide is vulnerable unless they manually override ARCADE_WORKER_SECRET.