FILE PHOTO: Silhouettes of laptop users are seen next to a screen projection of Facebook logo in this picture illustration
INTERNATIONAL -  Facebook has discovered a security flaw affecting about 50 million user accounts which could have allowed attackers to take over those accounts, the social networking company said on Friday.

Facebook, which has more than 2 billion monthly active users, has since fixed the vulnerability and informed law enforcement, it said.

So, how do you know if you have been one of the 50 million people affected by the security breach? Quite simply, Facebook would have already asked you to log out and back into your account again. 

Attackers stole Facebook access tokens through its “view as” feature, which they could then use to take over people’s accounts. “View as” allows users to see what their own profile looks like to someone else.

“We do not currently have any evidence that suggests these accounts have been compromised,” chief executive Mark Zuckerberg said in a Facebook post.

Facebook shares fell more than 3 percent in afternoon trading, weighing on major Wall Street stock indexes.