Facebook says more than 800,000 users may have been affected by a bug that unblocked people they previously had blocked.
The company said Monday that the bug was active between May 29 and June 5. While the person who was unblocked by this bug could not see content users shared with their friends, they could have seen things that were posted to a wider audience. Facebook says the problem has been fixed.
"People who were affected will get a notification on Facebook encouraging them to check their blocked list," Facebook's chief privacy officer wrote.
It's the second software bug in less than a month that the company has notified users about. In June, Facebook disclosed that a software bug led some users to post publicly by default regardless of their previous settings. That bug affected as many as 14 million users over several days in May.