What to Know
Facebook says 50 million accounts were potentially compromised by a hole in its code[hhmc]
The attackers, who are still unknown, may have used the exploit to get users' personal information[hhmc]
Facebook discovered the flaw on Tuesday and has notified law enforcement[hhmc]
Facebook said on Friday it has discovered a security issue affecting 50 million accounts, which could have let hackers take over the accounts and access users' personal information.
"Since weve only just started our investigation, we have yet to determine whether these accounts were misused or any information accessed. We also dont know whos behind these attacks or where theyre based," Facebook vice president of product management Guy Rosen said in a blog post.
Rosen said the company discovered the issue on Tuesday and notified law enforcement. The attackers exploited a hole in Facebook's code related to the "View As" function, which lets people see what their profiles look like to other users.
A total of 90 million users will have their access tokens reset, the company said, which means they will have to log back in the next time they try to use Facebook.
Shares in Facebook fell sharply on the news before rebounding somewhat, though they were still down 3 percent in midday trading.
This is a developing story.