RAGE is a proprietary engine that Rockstar Games has used for well over a decade. It's the studio's go-to engine for all of its games, including the biggest titles, such as Grand Theft Auto 5 and Red Dead Redemption 2.
Over the years, Rockstar has done an excellent job at updating the RAGE engine. In particular, Red Dead Redemption 2 looks like a game built for next-gen consoles even though it came out in 2018. But, it's not without its faults. The award-winning open-world western action game suffered from the same clunky movement systems and shooting that older Rockstar games did.
In an earlier leak, we came across info suggesting Rockstar will use an updated version of the RAGE engine for GTA 6, one that will address the issues that Red Dead Redemption 2 had and build on its strengths, such as how NPCs in the game appeared to organically interact with the world around them.
Now, the massive GTA 6 hack appears to confirm this.