Facebook Reveals Hackers Exposed Personal Information of 50 Million Users

An attack on Facebook‘s computer network exposed the personal information of about 50 million users, the social media platform said Friday.

The company discovered the breach earlier this week and found that attackers exploited a feature in Facebook’s code that allowed them to hack into and take over accounts. Facebook fixed the leaky code and reportedly notified law enforcement officials.

Friday morning, more than 90 million Facebook users were required to log out of their accounts — either on their phones or on their computer — as a safety measure for compromised accounts.

“On the afternoon of Tuesday, September 25, our 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,” wrote Guy Rosen, VP of Product Management, in a company blog post.

The company continued that its investigation is “still in its early stages.” The bug, more specifically, was a vulnerability in the “View As” feature, which allows people to see what their own profile looks like to someone else.

“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 explained.

Facebook said it’s reset those access tokens as well as an additional 40 million accounts. It said users will be notified once they log in.

The additional 40 million accounts that Facebook logged out and reset the passwords for have been subject to a “View As” look-up in the past year, Rosen explained. “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 has turned off the “View As” feature while it conducts its security review.

Rosen also wrote that the company doesn’t know whether the accounts were misused or if any information was accessed. “We also don’t know who’s behind these attacks or where they’re based.”

“If we find more affected accounts, we will immediately reset their access tokens,” said Rosen.

“People’s privacy and security is incredibly important, and we’re sorry this happened,” the blog post continued. “It’s why we’ve taken immediate action to secure these accounts and let users know what happened. There’s no need for anyone to change their passwords.”

Rosen said that if users affected by the hack are having trouble logging back into Facebook (perhaps if they’ve forgotten their password), they should visit the site’s Help Center.