Facebook says 50 million accounts affected by security breach

CHICAGO (WLS) -- Facebook said Friday they have discovered a "security issue" affecting 50 million user accounts.

In a security update, officials at Facebook said their engineering team discovered the issue on Tuesday. They said that while their investigation is in the early stages, hackers exploited a vulnerability in their code that impacted the "View As" feature that allows users to see their Facebook page as others would see it.

Facebook officials said hackers then stole access tokens - which allow users to stay logged in and not re-enter their password every time they use the app - which could be used to take over the accounts.

Officials said they have fixed the vulnerability. They also contact law enforcement about the breach.

Officials also said they reset the access tokens of nearly 50 million accounts they know were affected in the breach. They said they reset an addition 40 million access tokens as a precaution. Around 90 million people will have to log back into Facebook or any of their apps that use Facebook login, the company said.

The company has also temporarily turned off the "View As" featured as their review continues.

The investigation is ongoing.