How Should I Destroy a Website Which Is Vulnerable to CSS?

So there are a few scam generator websites for (mostly) online games, and all you have to do is enter your name and amount of stuff you want to get. So most of these are vulnerable to CSS, I wrote to where I need to type my name and it just executed it (so it said HI).

But I want to destroy that website so nobody will get scammed :d

Is it possible? How?

Thank you!