But the question is how did they get there. I find it unlikely that two mods, both of whom are prolific posters, would both choose the same day to post a malicious redirector to the same site instead of a safe link.
My thinking is that somehow the Kitty Kats system injected the redirectors there when they were posted. Why it would do that is what I'm wondering. Is it possible someone found a vulnerability in XenForo and is exploiting it?