800,000 Facebook users affected by bug that caused temporary unblocking

Facebook said on July 3 that a bug had unblocked some people that users had blocked, affecting over 800,000 users. The company said the issue has now been fixed and the users have been blocked again.

The bug, which also affected the company's Messenger service, was active from May 29 to June 5, the company said in a blog post.

Unblocked users could not view content shared with friends, but could view content shared with a wider audience, for instance a photo shared with friends of friends.

The company clarified that the unblocking did not renew friend connection. Blocking automatically unfriends a person on the platform.

But an unblocked user could still contact the person who had blocked them on Messenger, Facebook added.

"83% of people affected by the bug had only one person they had blocked temporarily unblocked; and someone who was unblocked might have been able to contact people on Messenger who had blocked them," Facebook said in its post.

Facebook has apologised for the issue and said it will notify affected users to recheck their blocked list.

"We know that the ability to block someone is important — and we'd like to apologize and explain what happened," Facebook said in the blog.

The company had not provided details on what caused the bug. But in a response to a TechCrunch, Facebook said the bug deleted some of the associations, or ways in which visible data is stored.

A bug mistakenly deleted some of these associations across Facebook and Messenger, which caused blocks to be lost.

— Facebook (@facebook) July 2, 2018