The GTA 6 trailer was leaked by a threat actor who goes by the alias Skenkir.

He purchased access to a YouTube admin panel which allowed him to view the unlisted video early.

Incident Timeline: December 4, 2023

20:50 UTC - Skenkir first mentions having new GTA trailer and shares YT admin panel screenshot on Telegram
20:58 UTC - Skenkir shares screenshot from trailer showing GTA release date
21:58 UTC - Skenkir leaks trailer on X
23:10 UTC - Rockstar verifies the leak