Facebook posted a security update that describes a security issue that occurred on September 25, 2018 that affected nearly 50 million accounts.
An excerpt from Facebook security update posted on Friday:
“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.”
Facebook has fixed the issue, but as a precaution has reset access tokens for the 50 million accounts and an additional 40 million accounts that have been subject to a “View As” look-up over the last year.
As a consequence, nearly 90 million user accounts will now have to log back in to Facebook or any other app that uses their Facebook Login.
Facebook added the company is “temporarily turning off the ‘View As’ feature while we conduct a thorough security review.”
The company is continuing the investigation to determine impact and whether any Facebook accounts were misused or any information accessed.