Facebook held an all-employees meeting to discuss reports of a personal data breach affecting 50 million users.

Lawmakers in the United States and the U.K. are demanding the Silicon Valley social media giant answer questions about how it happened.

CGTN’s Mark Niu reports.

The U.K. firm Cambridge Analytica created a Facebook app called This is Your Digital Life. It actually paid users to take a personality test.

But the app is believed to have also collected more information such as a user’s “like history.” It also harvested data from the user’s friends. In the end, the app accessed personal information from an estimated 50 million users.

Facebook ended that avenue for access to friends’ data in 2014.

The allegations say the data was still accessible during the 2016 presidential campaign. A Cambridge Analytica executive quoted in the British media said his firm used the information to help then candidate Donald Trump.

“Cambridge Analytica is built on this model,” said Ahmed Banafa, a Cyber Security Expert at San Jose State University. “They mentioned that within ten likes of a certain element or article, I can predict your answer more than your co-worker. Within 70, you can predict more than your friends, 150 more than parents. And with 300, more than your partners. I consider the ‘Like’ button the most significant invention in social media because it’s in a very liberal way, — everywhere.”

Facebook said Cambridge Analytica’s work was supposed to be for academic purposes only.

But Soviet-born researcher, Aleksandr Kogan, who designed the app, has reportedly told colleagues that wasn’t the case.

Amid the controversy, Cambridge Analytica has suspended its CEO. Facebook says it’s hired a digital forensics firm to investigate the data breach. Federal Trade Commission fines are $40,000 per incident. Multiply that by fifty million users and Facebook could be on the hook for $2 trillion.

In an age where personal data is seemingly collected everywhere, security expert Banafa offers some advice.

“Don’t trust blindly the third party apps, especially if they are going to pay you. Because, if they pay you, that means they ask for more information,” said Banafa. “Number two: you go to your app setting on Facebook and you are going to see you can disable that. Uncheck many of the options there. And that will prevent Facebook from giving information from anyone who is asking for it.”