Rockstar Games released an update for GTA IV on Thursday, 09.02.2023. The update is 158 MB in size and has been in development and testing for some time.
The previous update removed the multiplayer aspects of the game.
Current Speculations
It is speculated that the current update is security-oriented and may be related to the Rockstar security incident of 2022. So far, no visible changes to the game have been discovered.