Facebook reported a major security breach yesterday, a breach which resulted in 50 million user accounts being accessed by unknown cyber attackers. The Facebook security breach is a major setback for the company already having a bad year facing security problems and privacy issues.

The officials do not know who was behind the Facebook security breach or where they were based. Facebook CEO, Mark Zuckerberg also admitted that the company does not know if any of the accounts were hacked were misused.

In the Facebook security breach, hackers were able to access data from millions of user accounts and the stolen data allows them to “seize control” of those accounts.

As a safety measure, Facebook has logged out of fifty million breached accounts along with another forty million accounts vulnerable to an attack. The company has asserted that users have no need to change the passwords of their accounts.

According to a blog post of the company, the Facebook security breach resulted from a bug in the “View As” feature. This feature allows a user to see how their profiles appear to others.

There was a vulnerability in the feature that allowed attackers to steal “access tokens”, in other words, digital keys through which people remain logged in. If the attackers have these tokens, they can seize control of the account.

If security experts are to be believed then the stolen access tokens would have allowed the attackers to have access to and view private posts and also post status updates or share posts. They would, however, not have access to the passwords.

The Facebook security breach reminded many of the much larger attack on Yahoo in 2013 in which three billion user accounts were compromised. Just to have an idea, three billion accounts are enough for half of the world. In the Yahoo case, the attackers stole information including names, email addresses, phone numbers, and security questions as well as the answers.

The Facebook security breach is yet another reminder that we are yet to find a viable and airtight solution to the rising privacy concerns.