According to Steam DB and several lengthy Reddit posts, source code for popular Valve titles CS:GO and TF2 was allegedly leaked. What does this mean?
Potentially, it could put your computer at serious risk if you log on to these games (and possibly other source-based games like Half Life 2 could be dangerous here as well), as theoretically hackers could gain information, access, and even run malicious programs on your PC via this exploit.
The serious takeaway is, don’t log on to these games until the issue has been addressed. We’ll update this post if/as news develops on that front.
Source: Game Informer PSA: Don’t Play Counter-Strike Or Team Fortress 2 Right Now