What if he imitated a game, something that you thought was a game you wanted? With malicious code in the background? So you get the game and he melts your computer.... Or what if you don’t download games, but some other person does and this guy releases a super virus, which eventually infects your computer one way or…

Corrected this for you.

“I found a major flaw in your security that could allow for malicious games to be thrown on steam with no oversight. Not only that, But you ignored my attempts to contact you about it. So I exploited the flaw in a completely safe manner to get your attention. Brought the flaw to your attention…