I would be surprised if safety was not very high on the list of priorities. Getting hacked is always a nebulous proposal but I think it is quite easy to describe the consequences of somebody being hurt or killed by your product.
"We need to add this feature to the car immediately!"
"We can't do that because it would mean we would have to re-test the codebase, meaning we'd have to test-drive the car for hundreds of thousands of miles."
"Can't we take a shortcut? I believe the change is quite innocent. And the competitor already has this feature."
Safety investment is a by-product of how much money you're likely to get sued for. (or in the case of airplanes, more a side-effect of regulations and preventing customers' fears from affecting sales)
I wonder how that will work out with e.g. self-driving cars.