Facebook briefly broke parts of the internet on Friday with users unable to access websites.
It appears the Facebook plugins found on thousands of web pages, which allow people to share or recommend articles, for example, were faulty.
Those visiting websites including Fairfax news sites, BuzzFeed, The Huffington Post, The Washington Post, CNN and more were instead directed to a Facebook error page with a message saying "An error occurred. Please try again later".
The problem appears to be fixed now, although Facebook has only offered a cryptic comment about what happened:
"For a short period of time, there was a bug that redirected people logging in with Facebook from third party sites to Facebook.com. The issue was quickly resolved, and Login with Facebook is now working as usual."
The issue highlights the dangers of relying on other sites for core functions; many sites even use Facebook Connect whereby instead of creating a new user account users can simply log in with their Facebook details.