Social media giant Facebook said on Friday, 28 September, that 50 million (5 crore) of its user accounts have been affected by a security breach. CEO Mark Zuckerberg’s account was among those compromised, reported AP.The company says hackers exploited the "View As" feature on the service. Facebook says it has taken steps to fix the security problem and alerted law enforcement.To deal with the issue, Facebook reset some logins, so 90 million people have been logged out and will have to log in again. That includes anyone who has been subject to a “View As” lookup in the past year.The California-based tech giant said that it doesn't know who was behind the attacks or where they're based. In a call with reporters on Friday, Zuckerberg said that attackers would have had the ability to view private messages or post on someone's account, but there's no sign that they did.The hack is the latest security headache for Facebook, which has been dealing with political disinformation campaigns from Russia and elsewhere since 2016.CBI Begins Probe Into Facebook Data Theft By Cambridge AnalyticaWe’re Taking Precautionary Measures: ZuckerbergFacebook CEO, Mark Zuckerberg said in a post on Facebook that the the breach was discovered on Tuesday and was patched on Thursday night.“As a precautionary measure, even though we believe we’ve fixed the issue, we’re temporarily taking down the feature that had the security vulnerability until we can fully investigate it and make sure there are no other security issues with it. The feature is called “View As” and it’s a privacy tool to let you see how your own profile would look to other people.”Mark Zuckerberg, Facebook CEOMeanwhile, Facebook’s shares fell by 3 percent to $163.78 in afternoon trading, reported Reuters.Facebook’s StatementRead the full statement issued by the company here:“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.”(With inputs from AP.) We'll get through this! Meanwhile, here's all you need to know about the Coronavirus outbreak to keep yourself safe, informed, and updated. The Quint is now available on Telegram & WhatsApp too, Click here to join.