The complex "immune system" that keeps the social network safe seems to have been acting quite strangely over the weekend, when Redditors noticed the system was preventing a seemingly harmless status from being posted:
Other internet sleuths jumped on the quirk, attempting to post the status "Everyone will know" without success.
Some even got this message in response...
It was weird: was Facebook censoring its posts? Had something sinister been registered to the phrase "Everyone will know"? What did everyone know that we didn't know.
A number of theories are still flying about - but Facebook's response is frustratingly vague. "This was a mistake with our spam filter and our engineers have resolved the issue," Melanie Ensign of Facebook security communications told The Huffington Post. "We're constantly updating the rules used by our spam-fighting engine and this particular phrase erroneously got caught in the mix."
So, without sharing details on exactly how their spam filters work (they don't want people taking advantage of them), Facebook has hinted that some phrases are enough to get banned by its internal algorithms.
Facebook is complicated. Not in a 'Friends With Benefits' kind of way but in the sense that it manages to make the social interactions of several hundred million people pretty damn easy, whilst also simultaneously blocking out the activities of individuals and groups looking to manipulate or take advantage of it.
FYI - There's no point heading to Facebook and punching in "Everyone will know" - it's been working for the last day or two, although if lots of people start doing it again we'd assume it'll probably break again.
If you do see someone posting it though we recommend you respond with this...