Facebook has announced that an attack on its computer network has resulted in data leak from nearly 50 million users.
The company said that on September 25, its engineering team “discovered a security issue affecting almost 50 million accounts.”
According to Facebook, attackers exploited a feature that 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,” said the company in a press release.
“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.”
Facebook says it has reset the access tokens of nearly all the 50 million accounts affected to protect their security. It is also taking a precautionary step of resetting the access tokens for another 40 million accounts.
As a result, 90 million users will have to log back into Facebook or any other apps that use a Facebook login.
The company is also taking the step to temporary turn off its “View As” feature while it conducts a security review.
The company says that there is no need for anyone to change their passwords. But people who are having trouble logging back into Facebook — for example, because they’ve forgotten their password — should visit their Help Center.
“People’s privacy and security is incredibly important, and we’re sorry this happened,” said the company.
“It’s why we’ve taken immediate action to secure these accounts and let users know what happened.”