Facebook disclosed a bug this week that affected about 800,000 users by unblocking at least one person on that user’s block list for around one week.
Writing in a blog post, Erin Egan, the company’s chief privacy officer, said the bug was active between May 29th and June 5th.
It did not re-establish friend connections between any of the affected users and the blocked individuals, Egan says, but it did allow those previously blocked users to see posts shared to a wider audience, like photos shared with friends of friends.
Content shared with the friends-only preference would not have been accessible to the unblocked person.
Still, blocked users may have been able to re-send friend requests if they happened to notice they were suddenly unblocked.
Egan also confirmed that unblocked users were potentially able to send messages via Messenger to people who presumably did not want to interact with them at all.
