I think mnlfrnnds04 (Who got 44 Successful hacking attempt) tried to hack his submission (using another user account) http://www.codeforces.com/contest/244/submission/2573465
You can see another submissions: http://www.codeforces.com/contest/244/submission/2573346 http://www.codeforces.com/contest/244/submission/2573196 ...
Oh, really?? You one, who see it.
I think so, too.
You can write a private message to round's author's or Gerald. Anyway, I think they noticed this too and they'll check it soon.