"A virus has been detected in your driving software. Please upgrade now to remove this threat" ... and the consequences are potentially a lot more damaging than PCs.

When the target gets big enough, it will happen. And how to protect against this, when we don't really understand the weaknesses yet - a rogue radar/lidar imitator sending false echoes, strong EM fields messing with electronic components - it could even be an intermittent connection fault in a communications bus. Plenty of unknown unknowns in this field.