From hackread.com
Earlier today, the source code for Counter-Strike Global Offensive (CS:GO) and Team Fortress 2 (TF2) were leaked on 4chan and uploaded on Torrent sites for free download.
It all started when a Reddit account going by the online handle of /iShaugrrz published a screenshot displaying several compressed files. The Redditor claimed that these files contained unreleased source mods, CS:GO source code as of Operation Hydra and TF2 code as of Jungle Inferno.