Facebook said as many as 50 million “access tokens” may have been exposed. In particular:
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. 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.
….we have reset the access tokens of the almost 50 million accounts we know were affected to protect their security. 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. 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.
Before this problem, Facebook user data was shared with an outside company in March, which caused some members to be critical of its motives, and its willingness to protect their information.
Facebook has also been attacked because outsiders have used the network to influence elections (particularly the 2016 presidential election) and spread hate speech. No one outside Facebook knows the effects of these on membership, but they cannot be positive.
In the last year, there have been more and more reasons for people to leave Facebook. Now, there is another one.