Social media giant Facebook Inc (FB.O) on Friday admitted a security breach affected 50 million accounts. Facebook said that hackers stole digital login codes allowing them to take over nearly 50 million user accounts in its worst security breach ever given the unprecedented level of potential access, adding to what has been a difficult year for the company’s reputation.
In a statement released Friday, the company said that attackers could use Facebook’s “view as” tool – which lets a user see what their profile looks like to other users – to steal other users’ access tokens – digital keys that allow a user to stay logged into the social network without re-entering their password every time.
Facebook, which has more than 2.2 billion monthly users, said it has yet to determine whether the attacker misused any accounts or stole private information. It also has not identified the attacker’s location or whether specific victims were targeted. Its initial review suggests the attack was broad in nature.
Chief Executive Mark Zuckerberg described the incident as “really serious” in a conference call with reporters. His account was affected along with that of Chief Operating Officer Sheryl Sandberg, a spokeswoman said.
Shares in Facebook fell 2.6 percent on Friday, weighing on major Wall Street stock indexes.
Facebook made headlines earlier this year after profile details from 87 million users was improperly accessed by political data firm Cambridge Analytica. The disclosure has prompted government inquiries into the company’s privacy practices across the world, and fueled a “#deleteFacebook” social movement among consumers.
U.S. lawmakers said on Friday that the hack may boost calls for data privacy legislation.
The United States should launch a probe into the massive hack of Facebook that affected 50 million accounts, Senate Intelligence Committee Vice Chair Mark Warner said in a press release.
Earlier in the day, Facebook said hackers exploited a vulnerability in the social media platform’s code to use the “View As” feature to control accounts.
“The news that at least 50 million Facebook users had their accounts compromised is deeply concerning,” Warner said on Friday. “A full investigation should be swiftly conducted and made public so that we can understand more about what happened.”
“This is another sobering indicator that Congress needs to step up and take action to protect the privacy and security of social media users,” Democratic U.S. Senator Mark Warner said in a statement.
Federal Trade Commission Commissioner Rohit Chopra on Twitter said “I want answers” with a link to a Reuters story on the breach.
Facebook’s latest vulnerability had existed since July 2017, but the company first identified it on Tuesday after spotting a “fairly large” increase in use of its “view as” privacy feature on Sept. 16, executives said.
“View as” allows users to verify their privacy settings by seeing what their own profile looks like to someone else. The flaw inadvertently gave the devices of “view as” users the wrong digital code, which, like a browser cookie, keeps users signed in to a service across multiple visits.
That code could allow the person using “view as” to post and browse from someone else’s Facebook account, potentially exposing private messages, photos and posts. The attacker also could have gained full access to victims’ accounts on any third-party app or website where they had logged in with Facebook credentials.
“The implications of this are huge,” Justin Fier, director of cyber intelligence at security company Darktrace, told Reuters.
Guy Rosen, the Facebook vice president overseeing security, said the flaw was “complex” in that it resulted from three failings.
A video upload feature should not have displayed on a user’s profile page when accessed through “view as,” Rosen told reporters on a conference call. That alone would not have been problematic except that the video feature wrongly triggered the placement of the powerful login code. And it placed the code not for the “view as” user, but for who they were pretending to be.
Facebook fixed the issue on Thursday. It also notified the U.S. Federal Bureau of Investigation, Department of Homeland Security, Congressional aides and the Data Protection Commission in Ireland, where the company has European headquarters.
The Irish authority expressed concern in a statement that Facebook has been “unable to clarify the nature of the breach and risk to users” and said it was pressing Facebook for answers.
Facebook reset the digital keys of the 50 million affected accounts, and as a precaution temporarily disabled “view as” and reset those keys for another 40 million that have been looked up through “view as” over the last year.
About 90 million people will have to log back into Facebook or any of their apps that use a Facebook login, the company said.
Two Facebook users sued the company over the breach in federal court in California on Friday.
More than 6,000 users complained about the breach on Zuckerberg’s Facebook page.
“I’m so scared now. All my activities are on Facebook,” Mohammad ZR Zia, a 25-year-old college student in Kuala Lumpur, Malaysia, who has been using the social media platform since 2009, told Reuters. His account was logged out earlier on Friday.
The level of concern expressed on Facebook was enough that the company’s automated system temporarily blocked sharing of some articles about the breach.
“Our security systems have detected that a lot of people are posting the same content, which could mean that it’s spam,” a message told users. Facebook later apologized for the misfire.
Facebook has suffered narrower breaches before.
In 2013, Facebook disclosed a software flaw that exposed 6 million users’ phone numbers and email addresses to unauthorized viewers for a year, while a technical glitch in 2008 revealed confidential birth-dates on 80 million Facebook users’ profiles.
Below is the update from Facebook:
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.
Here is the action we have already taken. First, we’ve fixed the vulnerability and informed law enforcement.
Second, we have reset the access tokens of the almost 50 million accounts we know were affected to protect their security. We’re also taking the precautionary step of resetting access tokens for another 40 million accounts that have been subject to a “View As” look-up in the last year. As a result, around 90 million people will now have to log back in to Facebook, or any of their apps that use Facebook Login. After they have logged back in, people will get a notification at the top of their News Feed explaining what happened.
Third, we’re temporarily turning off the “View As” feature while we conduct a thorough security review.
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.
People’s privacy and security is incredibly important, and we’re sorry this happened. It’s why we’ve taken immediate action to secure these accounts and let users know what happened. There’s no need for anyone to change their passwords. But people who are having trouble logging back into Facebook — for example because they’ve forgotten their password — should visit our Help Center. And if anyone wants to take the precautionary action of logging out of Facebook, they should visit the “Security and Login” section in settings. It lists the places people are logged into Facebook with a one-click option to log out of them all.
Additional Technical Details
Here are some additional technical details about the security issue described above.
Earlier this week, we discovered that an external actor attacked our systems and exploited a vulnerability that exposed Facebook access tokens for people’s accounts in HTML when we rendered a particular component of the “View As” feature. The vulnerability was the result of the interaction of three distinct bugs:
First: View As is a privacy feature that lets people see what their own profile looks like to someone else. View As should be a view-only interface. However, for one type of composer (the box that lets you post content to Facebook) — specifically the version that enables people to wish their friends happy birthday — View As incorrectly provided the opportunity to post a video.
Second: A new version of our video uploader (the interface that would be presented as a result of the first bug), introduced in July 2017, incorrectly generated an access token that had the permissions of the Facebook mobile app.
Third: When the video uploader appeared as part of View As, it generated the access token not for you as the viewer, but for the user that you were looking up.
It was the combination of these three bugs that became a vulnerability: when using the View As feature to view your profile as a friend, the code did not remove the composer that lets people wish you happy birthday; the video uploader would generate an access token when it shouldn’t have; and when the access token was generated, it was not for you but the person being looked up. That access token was then available in the HTML of the page, which the attackers were able to extract and exploit to log in as another user.
The attackers were then able to pivot from that access token to other accounts, performing the same actions and obtaining further access tokens.
To protect people’s accounts, we’ve fixed the vulnerability. We have also reset the access tokens of the almost 50 million accounts we know were affected and we’ve also taken the precautionary step of resetting access tokens for another 40 million accounts that have been subject to a View As look-up in the last year. Finally, we’ve temporarily turned off the View As feature while we conduct a thorough security review.