Facebook reports security breach affecting 50 million accounts

On the afternoon of Tuesday, September 25, the Facebook engineering team discovered a security issue affecting almost 50 million accounts. They are taking this incredibly seriously and wanted to let everyone know what’s happened and the immediate action they have taken to protect people’s security.

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. 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.

Here is the action we have already taken.

1. They have fixed the vulnerability and informed law enforcement.

2. They have reset the access tokens of the almost 50 million accounts we know were affected to protect their security. They are 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. 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.