Facebook revealed that a “software bug ‘unblocked’ some people who had previously been blocked by another user, meaning the unblocked user could suddenly see some posts from the person who blocked them. The bug also meant that the person who had been blocked may have been able to reach out via Messenger to the person who blocked them, Facebook
said in a blog post. The bug affected 800,000 users and was live for about a week at the end of May and early June.”
—