Dockhand: Unauthenticated container exec via WebSocket upgrade

Dockhand is a Docker management application. Prior to 1.0.34, the in-browser container terminal endpoint /api/containers/<id>/exec does not enforce authentication on the WebSocket upgrade request. When an unauthenticated attacker has network reach to Dockhand, knows a target container ID, and targets a container with an interactive shell, the attacker can open a raw WebSocket terminal session and execute commands inside a known target container. This allows unauthenticated command execution inside the container, with possible host compromise when the container has sensitive mounts or privileged execution. This issue is fixed in version 1.0.34.