A major Facebook bug may have unblocked people you blocked

That ex you blocked on Facebook may have had access to your posts after all.

On Monday, Facebook revealed that a bug had affected the privacy settings of 800,000 users. The bug allowed users who'd been blocked on Facebook and Messenger to become unblocked — without those who blocked them knowing about it.

According to Facebook’s statement on the matter, 83 percent of people affected by this bug had “only” one blocked person temporarily unblocked. The other 17 percent of users had more than one person unblocked, thanks to the bug.

The unblocked users were not able to see content shared with the friends of those they'd been blocked by, and the bug “did not reinstate any friend connections that had been severed.” However, these unblocked users may have been able to contact someone over Messenger who had them blocked, and public post types that were not marked just for friends may have been made visible.

While the issue has now been fixed — all unblocked users are blocked once again — the bug was active for 8 days, impacting users between May 29 and June 5.

Facebook further clarified what happened on Twitter. According to the company, visible Facebook user data is stored in pairs called “associations.” The bug deleted some associations across Facebook and Messenger, and this caused the block settings for the affected users to be lost.

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When Mashable reached out for more information on the bug, a Facebook representative informed us that the bug was random and global, affecting users from all over.

In its original statement, Facebook pointed out why someone might want to block another user. From wanting to “take a break from someone posting content they find annoying” to more serious reasons like harassment and bullying, the blocking feature is deeply important to making Facebook a safe and secure place for its users.

With its statement, it's clear Facebook understands the possible ramifications of this bug. However, after many recent blunders, it seems the company still has action to take when it comes to its users' privacy.