The Lapsus$ hackers
https://www.bleepingcomputer.com/news/security/gta-5-source-code-reportedly-leaked-online-a-year-after-rockstar-hack/
The source code for Grand Theft Auto 5 was reportedly leaked on Christmas Eve, a little over a year after the Lapsus$ threat actors hacked Rockstar games and stole corporate data.
Links to download the source code were shared on numerous channels, including Discord, a dark web website, and a Telegram channel that the hackers previously used to leak stolen Rockstar data.