Facebook shares tumbled Friday, along with other social media stocks, after the company disclosed it had uncovered a security issue affecting about 50 million accounts, in which attackers stole Facebook access tokens through its “view as" feature. The attackers could use these tokens to take over people’s accounts.
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CEO Mark Zuckerberg, addressing the breach during a call Friday afternoon, called the attack a “serious issue.” During the call, the company said it is working with the FBI and is unsure who is behind the attacks.
Facebook’s "view as" feature allows users to see what their own profile looks like to someone else. The company said that it hasn’t determined whether the accounts were misused or if any information was accessed.
"Since we’ve only just started our investigation, we have yet to determine whether these accounts were misused or any information accessed," the company said in a blog.
The company said it has fixed the vulnerability in its code that allowed attackers access and has informed law enforcement. The company is temporarily turning off its “view as” feature while it conducts a security review.
Facebook has temporarily reset access tokens of almost 50 million accounts and as a precaution, is resetting access tokens for another 40 million accounts.
The social media giant said it will continue investing heavily in security.
Facebook shares have dropped 23 percent during the third quarter, which ends Friday.