Although you will to have to log back into your account, you do not have to change your passwords, Facebook added. Facebook has informed law enforcement agencies in the U.S. about the hack and are now investigating it.
Facebook could also face major fines in the European Union for their latest security breach.
The flaw has now been fixed, affected accounts have been reset and so have another 40 million as "a precautionary step", explained Facebook's VP of product management Guy Rosen. This feature lets people see what their profile looks to others, but a vulnerability in coding allowed the hackers to access tokens, which could then be used to take over people's accounts.
The issue was discovered on Tuesday 25 September by the company's engineering team.
A spokesperson for Ancestry told CNN, "While Ancestry does support Facebook login for some functions, we always require an additional Ancestry username and password to access sensitive account functions such as downloading your DNA data, changing your password, changing your email address or accessing payment information".
"Today's disclosure is a reminder about the dangers posed when a small number of companies like Facebook or the credit bureau Equifax are able to accumulate so much personal data about individual Americans without adequate security measures", Warner notified in a statement shortly after Facebook's disclosure, according to NASDAQ.com.
TransferWise, a money wire service that allows users to log in through Facebook, said its investigation was underway but that it had "no indication" that its customers had been affected.
Facebook, which has over 200 million users in India, counts the country among those with largest user bases globally. "As I've said before - the era of the Wild West in social media is over".
It is not a surprise that Facebook was hit with a class-action lawsuit after announcing its security breach on Friday.
You may have noticed that when you log into your Facebook account once, a security key (access token) is generated, which helps the app to login to the user's account next time without a password. This basically means if you signed up for Instagram or and any other platform using your Facebook account, hackers might have also gained access to your account on another platform.
The CEO of Facebook, Mark Zuckerberg, has testified before the Senate's Commerce and Judiciary committees earlier this year about the concern of the spread of misinformation on the platform during the presidential elections of 2016. More importantly, Facebook confirmed that hackers could have accessed any third-party account that you had logged into via Facebook.
Facebook is in particular accused of not having been vigilant enough on monitoring the content and authenticity of pages and political ads that it carries.
The year 2018 has been a tough sail for Facebook. He subsequently attempted to backpedal from his comments, which did not impress most of the leftist billionaire's critics.