GHSA-22qr-rp27-j9wm: PenPot MCP REPL server binds to 0.0.0.0 with unauthenticated /execute endpoint — RCE

PenPot's MCP REPL server binds to all network interfaces (0.0.0.0:4403) and exposes an unauthenticated /execute endpoint that runs arbitrary JavaScript code, allowing anyone on the network to achieve RCE (remote code execution, where an attacker can run commands on a system they don't own). The vulnerability exists because the server listen call omits a host argument, defaulting to 0.0.0.0, and the /execute endpoint has no authentication checks before executing user-supplied code.