Facebook just announced a security breach that has affected 50 million user accounts. Hackers took advantage of a system flaw that enabled them to take control over the accounts.

In a blog post published to the company’s website, it is stated that the breach was discovered this past Tuesday and it’s still under investigation. Facebook – whose users number over 2 billion – has notified law enforcement officials here in the United States and at their European headquarters in Ireland.

According to the post, hackers gained access through a feature called “View As” 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. . .”

Once engineers discovered the attack, they reset the access keys of all affected accounts and an additional 40 million accounts as a precautionary measure. Due to the reset, users are being asked to log back in to Facebook or any connected apps that utilize Facebook as log-in step.

The social media giant also issued an apology over the incident and has disabled the “View As” option while the investigation is underway. At this time, they are unsure who is responsible for the attack or how long the accounts were vulnerable.

If your account is part of the breach, you will notice that you need to log-in to Facebook on all platforms and there will be a notification on your account explaining what happened. Facebook encourages those who have concerns about their account security to sign out of all Facebook-related apps and/or change your password.

Were you one of the affected accounts? Is this your first time hearing of the breach? Do you have any other concerns about Facebook’s security?