It is a viral message that is getting surfaced on Facebook asking users to type 'BFF' in the comment section to check if their account has been hacked.
This is actually a hoax and a majority of people getting duped. This hoax came after the news broke out that data company Cambridge Analytica gained access to millions of Facebook users' data and allegedly used it to try to influence the 2016 US presidential race in favor of Donald Trump.
As per the message, if the term 'BFF' turned green, the account is safe, but if it remained black, the account was hacked. Some comments turned green due to a new Facebook update.