How Not to Index Membership and Subscription Profiles on Google (and other search engines)?
Please see http://prntscr.com/etfew3. Members and subscription profiles are indexed by Google. How to keep these links private and not indexed?
It's designed to allow Google to index. User profiles of all forum platforms are always available for index. I'm sorry but there is no way to restrict this with current wpForo version. We'll add this in our to-do list.
On my forum I enable a restriction for guests to view forum profile, so search crawlers see profile links but cann't to index them. Hope this helps.