But it is firewalled (between OBD port and the car, between internal buses,...). I won't say it's sufficiently locked down, but as we recently saw - not even Apple got that completely right - but there are several layers of protection(s) on the various communication bus-es and computers. At least on European Manufacturers.

I agree that this needs more hardening, but reading this comments one would get an idea that a 12 years old kid with a 10EUR dongle can hack any car. When in reality, stuff is a lot harder to do.