Companies are spending billions of dollars in r&d to build self driving cars and you think a hobbiest is going to modify his car with his own "aggressive" self driving system?
Hacks are not required to be sophisticated to be effective and people will find them. Maybe for example if you place a 1/4 inch of extra plastic in front of the front facing radar it'll make the car follow more aggressively then it's calibrated for, who knows! that's a made up example but I expect this stuff is going to happen as it already does.
Hobbyist.