Facebook is notifying 800,000 users affected by a blocking bug

Yesterday the social network giant Facebook started notifying 800,000 users affected by a blocking bug. The company has already fixed it.

When a Facebook user blocks someone, the blocked user will be not able to interact with him, this means that he will not see his posts, it will not able to start conversations on Messenger or add him as a friend. The blocked user may have also been able to contact the blocker via Messenger.

Facebook discovered a bug affecting its platform that allowed blocked users to interact with the accounts that decided to block them. As result, blocked users were able to see some of the content posted by individuals who had blocked them.

The issue was introduced on May 29, and the social network giant addressed it on June 5.

“Starting today we are notifying over 800,000 users about a bug in Facebook and Messenger that unblocked some people they had blocked. The bug was active between May 29 and June 5 — and while someone who was unblocked could not see content shared with friends, they could have seen things posted to a wider audience. For example pictures shared with friends of friends. ” wrote Facebook Chief Privacy Officer Erin Egan.

According to Egan, one a user has been blocked will not see content shared only with friends, but he may have been shown content shared with “friends of friends.

Egan clarified that blocking also automatically unfriends users if they were previously friends.

Below the details shared by Egan on this specific bug.

It did not reinstate any friend connections that had been severed;
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 has fixed the bug and everyone has been blocked again, the company is sending a notification t the affected accounts encouraging them to check their blocked list.

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Pierluigi Paganini

(Security Affairs – Facebook, bug)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.