What did the bug do?
When users post to Facebook, there is a menu option that dictates who sees that post. If the user chooses public, anyone can view that post. The other options limit the audience, with most users typically posting updates that reach their friends. Facebook remembers what setting you last chose and automatically selects it the next time you make a post.
However, between 18 and 22 May this year, the bug would set posts to “public” even if the user had, in the previous post, chosen something more private. If the user did not notice the setting had changed, they may have posted something publicly that was not intended for that wider audience.
Facebook said it estimates 14 million people did so – and so has started notifying users. In the meantime, it has reverted the audience for any affected posts to whatever setting the user had selected previously.
While relatively minor compared to recent issues facing the company, the glitch is another embarrassing slip-up for a firm already under heavy fire over privacy concerns. This week, it has been answering questions about the nature of data-sharing deals with handset makers including Chinese manufacturers Huawei and ZTE.
Those affected by this latest blunder will be shown a graphical notification soon, with the chance to review what posts may have been posted publicly by mistake.
A spokesperson told the BBC this method of communication might become more frequent as the network works on ways to be more transparent with users.