Earlier today, source code for Counter-Strike: Global Offensive and Team Fortress 2 started to circulate, alarming gamers and modders who worried that they could expose security flaws. At least one project shut down as a precaution. However, code for the game has been previously available, this leak just spread it much wider.

We have reviewed the leaked code and believe it to be a reposting of a limited CS:GO engine code depot released to partners in late 2017, and originally leaked in 2018. From this review, we have not found any reason for players to be alarmed or avoid the current builds. — CS:GO (@CSGO) April 22, 2020

According to Valve, in a statement posted from the CS: GO Twitter account, 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 2018” and found no reason for alarm among players. SteamDB operator Pavel Djundik suggested similar, saying it would probably provide “very little” help to cheat developers.