Comment 1 for bug 700580

What pages (listinfo, admin, admindb, ...) give this error?

This is a generic error issued whenever one of Mailman's CGIs throws an uncaught exception. In order to know what the problem is, we need to see the tracebacks and other information from Mailman's error log. The log is /usr/local/cpanel/3rdparty/mailman/logs/error .

I sincerely doubt that this is a security issue, but I will leave this marked private pending more information.