50 Million Accounts Affected By Huge Facebook Security Breach

If you use Facebook (and you probably do), you might want to be aware of a large-scale security breach.

Guy Rosen, VP of product management at Facebook, recently announced that the company discovered a major security issue.

Rosen says that on the afternoon of Tuesday, Sept. 25, Facebook's engineering team discovered a security issue affecting almost 50 million accounts.

"We're taking this incredibly seriously and wanted to let everyone know what's happened and the immediate action we've taken to protect people's security," he wrote in a statement.

"Our investigation is still in its early stages. But it's clear that attackers exploited a vulnerability in Facebook's code that impacted 'View As', a feature that lets people see what their own profile looks like to someone else."

Facebook says this allowed them to steal Facebook access tokens which they could then use to take over people's accounts.

“Access tokens are the equivalent of digital keys that keep people logged in to Facebook so they don't need to re-enter their password every time they use the app," Rosen says.

Facebook says it has fixed the vulnerability and informed law enforcement.

It also says it has reset the access tokens of the almost 50 million accounts it knows were affected.

"We're also taking the precautionary step of resetting access tokens for another 40 million accounts that have been subject to a 'View As' look-up in the last year," Rosen says.

"As a result, around 90 million people will now have to log back in to Facebook, or any of their apps that use Facebook Login. After they have logged back in, people will get a notification at the top of their News Feed explaining what happened."

Facebook is temporarily turning off the "View As" feature while it conducts a security review.

"This attack exploited the complex interaction of multiple issues in our code. It stemmed from a change we made to our video uploading feature in July 2017, which impacted 'View As. The attackers not only needed to find this vulnerability and use it to get an access token, they then had to pivot from that account to others to steal more tokens," Facebook says.

"Since we've only just started our investigation, we have yet to determine whether these accounts were misused or any information accessed. We also don't know who's behind these attacks or where they're based. We're working hard to better understand these details -- and we will update this post when we have more information, or if the facts change. In addition, if we find more affected accounts, we will immediately reset their access tokens."

Users who are having difficulty re-logging in to Facebook are asked to visit the company's help center.