Facebook Inc. had a software bug for 10 days in May that set the audience for people's posts to "public", even if they had meant to share them just with friends, or a smaller audience. Even if a user had set their default sharing option to "friends", the bug changed the setting for affected users to "public".
The flaw only affected Facebook's system for 10 days in May, but Facebook says it still plans to notify users who were impacted by the bug. "We'd like to apologize for this mistake".
Facebook said it will reach out to the users who are thought to have been affected by the bug.
Over the past few days, Facebook has been under scrutiny for giving Chinese company Huawei access to users' data, even though the USA government has held that company under suspicion in the past over its ties to the country's communist government.
Facebook told BleepingComputer that the "error occurred while we were building a new way to share featured items on your profile, like a photo".
The mishap comes on the tail of several privacy scandals involving the social network in recent months.
Facebook CEO Mark Zuckerberg was questioned for two days on Capitol Hill in April about the importance of user security. The message from Facebook urged users to "Please Review Your Posts", and gave them a link to a list of what they shared on Facebook while the bug was active.
"Starting today we are letting everyone affected know and asking them to review any posts they made during that time", Egan said.
Facebook also said Thursday it would end its data partnership with Huawei by the end of this week following a backlash over the Chinese phone maker's access to Facebook user data. If I limit a post's audience to just friends from high school, for instance, Facebook will make that the default audience setting on all of the posts I make from then on.
The tweet below shows the notification users will be receiving.