Privacy settings of about 14 million Facebook users were accidently changed due to a bug, leaving the possibility that messages on the social network were inadvertently publicly shared. Facebook users can use their settings to share messages with friends, a smaller group or with everyone.
When an user posts a message, the default privacy setting is used. When the user has chosen to only share posts with friends by default, the message is only shared with friends when the user hits the post button. However, users can also decide to change the privacy for each individual message, overriding the default setting.
Due to a bug in Facebook, the default privacy settings for messages were automatically changed. This caused, that between the 18th and 27th of May, each message for which the individual setting wasn’t changed, automatically became visible to everyone. This even happened despite the fact that each message was clearly marked as being visible for everyone. And it likely happened because a lot of users are so accustomed to their messages only being readable by a select group that they didn’t notice.
The bug was introduced together when a new feature was rolled out, according to social network site. The issue was resolved on the 22nd of May, but it took some time before Facebook changed all messages back to the correct privacy settings. Affected users can expect a message from Facebook notifying them about the issue.