The part they're messing with it's "just" the infotainment system. The autopilot system and a lot of other things are "protected" by a gateway.

You'd still need Tesla's signing key to rewrite the Autopilot software or mess up some more important components.

Now, the CID is still coordinating some parts of it - but AFAIK the car works also without that, to the point that you can simply reboot the infotainment system without losing control of the vehicle / Autopilot