UBB.threads PHP Forum Software Community Forums UBB.classic UBB.classic 6 Support Spam exploit

If you could find out exactly which script they accuse of being the culprit, that would be helpful.

If it's in the UBB's CGI directory, but does not start with "ubb" or "cp", then it is not part of the UBB. You may have a mailform script there as well.