My forum has been hacked

[nwind]

My forum at http://www.jouster.com/forums has been hacked. The hacker placed garbage at the top of each thread page, with the rest of the page normal once you scroll down. I have gone through my templates and everything else but only the website index page had a recent change date. I fixed that page but it had no effect on the forum problem.

I have gone through the templates and can't find anything wrong. I really don't know where to look. Can someone please help?

--------------- Added 1435256154 at 1435256154 ---------------

Got the answer from support and was able to fix it. I don't know how they got into it, but they altered my displaypost.php file, should anyone else have this problem.

[ForceHSS]

Talk to your host to see how they got in so you can stop it happening again

[Dave]

Be sure that no other files were modified and that no were backdoors were placed on your server.
Checking each plugin is also a good thing to do for malicious code.