Facebook apologized Monday for temporarily unblocking users that people had blocked on the social network—a glitch that could have affected more than 800,000 users. The company revealed the slip-up in a blog post, saying the bug affected users between May 29 and June 5.
When you block someone on Facebook, they’re unable to see anything you post. Because of the glitch, the people who were unblocked could see content that users shared with “friends of friends.” They could also use Facebook Messenger to contact people who had blocked them. They could not see content shared with friends only. They also could not refriend anyone who had blocked them.
Facebook made the announcement after it had already resolved the issue, restoring everyone’s blockings. People who were affected by the glitch will receive a notification nudging them to check their blocked list. Most people impacted by the bug had only one person temporarily unblocked, according to the company.
Blocking allows users to prevent people from seeing their posts, messaging them, or adding them as a friend. It’s a useful tool for users facing bullying, harassment, or stalking on the platform. The company rolled out new tools last year to make it more difficult for harassers to continue contacting people who had blocked them.
Facebook became aware of the bug on May 31 but it took until June 5 to restore the blocks, according to a company representative. It then took time to determine how many people had been impacted and build the notification messages.
This glitch comes after a software bug in May that caused as many as 14 million users to post publicly by default, regardless of their previous settings. And it’s a good reminder that no matter how tightly you set your Facebook permissions, they’re always just a string of bad code away from being pried loose.