Two popular GTA V mods, Angry Planes and No Clip, have been shown to contain malware by various sources. The claims first appeared on the GTA forums, where user aboutseven put together a fairly convincing case for how he received a virus on his PC from using one of these GTA V mods. The story has seemingly been confirmed in a post on GTA5-Mods.com, which details the events leading up the discovery and the next steps that users should take. Essentially, if you have used either of these GTA V mods you should take steps to remove them and the malware, and then start changing your passwords as they may have been compromised.
Apparently thousands of users downloaded the Angry Planes mod off of the GTA5-Mods website. Multiple websites, such as Kotaku and PC Gamer highlighted the mod, which spawns numerous airplanes that all try to attack the player. The mod has since been removed and GTA5-Mods is beefing up their verification process to avoid a similar situation in the future.
If you feel that you might have been infected then immediately remove the mods and begin running a good anti-virus program. Malwarebytes is a popular solution and should help take care of the issue.