Mambo [http://www.mamboserver.com/. only Joomla! will be evaluated. I hate forks.
I have just found out that the post has been replied to. Your forum must not have notification on by default.
That's why i disagree with you.Can you analize what do you mean by telling us : " a huge security related forum"?
I don't believe that if one cms has a section on his community forum called "security" then the summary is that this CMS is secure!
Security problem - one of the big CMSes (WP, Drupal, Joomla), I won't tell you which, is so unsecure they have a large forum just for security issues.