If there is actually a problem with the forum, MalwareBytes can
collect a substantial bounty. But they're probably just wrong. Anti-malware companies make money by scaring users into thinking that everything around them is dangerous. The forum has previously been blocked by anti-malware software because you can find download links to stealth mining software here.
Doesn't explain how I (MBAM PRO user) see the warning, but regular MBAM users do not? atleast investigate the issue. could have slipped some malware under your nose into the server for all you know.