The full GTA V source code has been leaked The leak contains GTA V source code and stuff from Bully 2 and GTA VI Leaked in a discord server by a random British guy in the 360 modding community known to get sued by Rockstar multiple times
"Now i am expecting a open source version of gta to arrive soon on linux natively . Tired of playing supertuxcart."
Here is the source. Another one.
Or you hire an intelligent, capable, and professional pen tester. They'll find the same holes that the nutcase will, they'll document them, and they'll do it without breaking things.