Code is from a 2018 leak.

Update (April 22, 2020 at 9:18PM ET): According to a statement issued to PC Gamer from Valve, the leaked code is only for CS:GO, but it does include "very old pieces of Team Fortress 2." Valve says that they will continue to investigate.

Valve also says that after an initial review of the leaked code they "believe it to be a reposting of a limited CS:GO engine code depot released to partners in late 2017, and originally leaked in...