Also a well know problem for chatrooms..blogs...and discussion forums. Consequently, while apt that a lone wolf type can gain an access... so too any terrorists group interested in recruiting and or facilitating communications through what appears as an innocuous source.
Be aware of this and report the same to your LE agencies. Non-English speaking threads-subs on the aforementioned are usually the greatest target for infiltration. Any native speaker actively monitoring these or participating there should report this or any violation of the CoC to the administration immediately.
Do not mistake this as not serious...as hackers will for a number of reasons attempt to jack a site.
CV