Tilt: Missing authentication on the network-exposed Tilt HUD server

Tilt defines dev environments as code for microservice apps on Kubernetes. From 0.20.8 through 0.37.3, the Tilt HUD HTTP server registers handlers on a gorilla/mux router with no authenticating middleware. When the HUD is bound to a non-loopback address, an unauthenticated network caller can trigger developer-defined resources, tamper with Tiltfile arguments, read full engine state including the session token, and invoke apiserver resources through the token-attaching /proxy handler. This issue is fixed in version 0.37.4.