Short version:

• There are no active Remote Code Execution exploits.
  
• The leaked code is from 2018.
  
• It's safe to play the game.
  
• TFP has been up, is up, and will remain up.
  
• https://twitter.com/TeamFortress/status/1253186403900420098

Remember, folks: 4chan posts, unaffiliated Twitter accounts, random online forums, "I heard from my friend who knows a guy", the unsubstantiated word of cheating tool developers, and screencaps of posts from random Discord servers are not trustworthy sources of information.