My website [url removed, login to view] was hacked and messed up. I contacted vbulletin and they said the following.
1) Fixing the damage:
You need to restore a backup from before the forum was hacked. If you don't have a backup then you should ask your host if they have one.
2) Preventing future attacks:
Here are some security tips to help prevent this in the future:
[url removed, login to view]
3) Finding out exactly how they hacked you:
If an admin or mod account was hijacked then you might find evidence of their activities in the vBulletin logs:
Admin CP -> Statistics & Logs
It can be difficult to track down exactly how the hacker got in. You will need to consult with your host to examine the server logs for evidence of intrusion. Otherwise you can just follow the above security tips to help prevent future attacks.
vBulletin Support Staff