FACEBOOK BUG MADE UP TO 14 MILLION USERS' POSTS PUBLIC FOR DAYS

The bug, which reportedly occurred while Facebook was testing a new feature, went live on May 18. Facebook told CNN, which first reported the issue, that it began rolling out a fix on May 22. The bug was fully corrected by May 27. If some of your posts have been affected by the bug, Facebook says they should now have been reverted back to your normal sharing settings.
Typically, if you share something to Facebook, the privacy settings of that post default to the last ones you used. For example, if you share a photo and set it only to be seen by your friends, then the next time you post something, Facebook will assume you want to share it with the same audience. Those affected by the bug had their default setting changed instead to "public." That could be potentially harmful if you shared sensitive information, like an address or phone number, assuming only friends could see it. Likewise, Facebook also allows you to exclude specific friends, like an ex-partner, from seeing your posts. If this glitch affected you, those people could have seen your posts.