Around 90million Facebook users were logged out of their accounts today.
The social media site has revealed hackers managed to take over 50 million Facebook user accounts earlier this week.
The attackers are believed to have exploited a “vulnerability” in Facebook’s code.
This affected “View As”, a feature that lets people see what their own profile looks like to someone else.
Hackers were then able to steal Facebook access tokens so they could then take over people’s accounts.
Should you delete your Facebook account after hack?
Guy Rosen, Facebook’s VP or Product Management, said in an online post that the vulnerability has been fixed.
Users should hold fire before making the permanent decision to delete their accounts, as Rosen added that any more affected accounts were found, Facebook will immediately reset their access tokens.
He wrote: “On the afternoon of Tuesday, September 25, our engineering team discovered a security issue affecting almost 50 million accounts.
“We’re taking this incredibly seriously and wanted to let everyone know what’s happened and the immediate action we’ve taken to protect people’s security.
“Our investigation is still in its early stages.
“But it’s clear that attackers exploited a vulnerability in Facebook’s code that impacted “View As”, a feature 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 that keep people logged in to Facebook so they don’t need to re-enter their password every time they use the app.”
Rosen added: “This attack exploited the complex interaction of multiple issues in our code. It stemmed from a change we made to our video uploading feature in July 2017, which
impacted “View As.”
“The attackers not only needed to find this vulnerability and use it to get an access token, they then had to pivot from that account to others to steal more tokens.
“Since we’ve only just started our investigation, we have yet to determine whether these accounts were misused or any information accessed.
“We also don’t know who’s behind these attacks or where they’re based. We’re working hard to better understand these details — and we will update this post when we have more
information, or if the facts change. In addition, if we find more affected accounts, we will immediately reset their access tokens.”