The journalist driver was in on it. I would still not rate that as a "prank". I'd be way too worried about collateral damage resulting from it to take any part in such a stunt.

Honestly, I still have issues with that story. Either someone shouldn't be allowed to put computers in cars or someone is lying.

I almost refuse to believe it's possible to jump from the entertainment system to the computers controlling the car. Designing a car where those two systems are connected in any way other than maybe power and one-way signalling from the car to the entertainment system would be reckless to an almost criminal extend. Honestly, what engineer would suggest something like that?

The guys who did the hack chose the Jeep exactly for this reason -- an unregulated data pipe between the entertainment computer and the critical-systems computer. They analysed hundreds of cars and chose the worst-designed one they could find.