Facebook suffered a security bug on Thursday that affected a large number of users worldwide. The issue came to the spotlight when users started reporting in Facebook developers forum that their posts were mysteriously disappearing. The bug blocked people from sharing links to content outside of Facebook, and new links were blocked from posting.

Facebook Bug

The bug appeared on Facebook’s image-scraping tool

The bug was removing links for “violating the security policy.” The issue appeared on the social networking giant’s image-scraping tool that automatically pulls images from shared links. Initially, some users accused Facebook of selective censorship as their links to stories about the Baltimore riots mysteriously disappeared. But soon it became clear that it was a widespread issue.

Users trying to post new links were served a security warning that the link they were attempting to share were “unsafe” and should remove the link to continue. Others who clicked on existing links were also met with similar security warnings. Facebook engineers started working to fix the bug immediately. A Facebook spokesperson said in a statement that the issue had been fixed by Friday morning.

Facebook restores most of the deleted posts

By Friday morning, most of the removed posts were restored. A company spokesperson said that an error in Facebook’s system that blocks bad links “incorrectly marked some URLs as malicious or inappropriate.” Due to this, some posts were blocked completely, while some existing ones were hidden. The social networking giant said that the issue had been resolved, and its engineers were unblocking the remaining blocked URLs.

It’s not the first time Facebook website has experienced glitches that affected a large number of users. In January, Facebook and Instagram sites were down for about four hours after a reported hack. A hacker group called Lizard Squad had taken responsibility for the outages. But Facebook had quickly rejected Lizard Squad’s claims, saying that the issue was caused by “a change that affected our configuration systems.”