Overnight, many Facebook users were returned to groups to which they had previously belonged, and in some cases, were apparently granted access to groups of which they had never been a member.
The glitch, which has been confirmed by Facebook, means that content shared within the group was exposed to other Facebook users.
“I am admin of a secret group and had deleted a few members sometime back. But now they are again being auto added, showing as new members without any admin authorization,” Munaf Ali said in the Facebook community forums.
The users added to the groups were also surprised to see the content.
“It’s 3 a.m. I was asleep and my phone suddenly tells me I have 50 notifications from groups I somehow joined while I was sleeping,” said user Mary Langley Pettit.
“I should not have been re-added to these groups without my permission,” said Mike Olson.
Facebook says it is working to resolve the issue.
“In the meantime, we are rolling out a short-term fix for all closed groups that will make the content of those groups inaccessible to the re-added members,” a spokeswoman said.
The company did not say when the problem would be fixed.
Updated at 7 p.m. with comments from Facebook.
Image: Annette Shaff / Shutterstock.com