Users will find out today if their data was compromised.

Facebook (NASDAQ: FB) will contact the 87 million users on Monday who’s data was shared with Cambridge Analytica in the company’s data breach.

The social media giant will share a detailed message on the newsfeeds of those affected. Approximately 70 million users who were affected are in the US, with affected users also in the UK, Australia and the Philippines.

Cambridge Analytica, worked with Donald Trump’s election team and acquired the profiles of millions of US citizens, using the data to create a new software program to predict and influence voters. 

“I know that Facebook is now starting to take steps to rectify that and start to find out who had access to it and where it could have gone, but ultimately it’s not watertight to say that, you know, we can ensure that all the data is gone forever,” said Cambridge Analytica whistleblower Christopher Wylie in an interview with NBC on Sunday.

“We exploited Facebook to harvest millions of people’s profiles. And built models to exploit what we knew about them and target their inner demons. That was the basis the entire company was built on,” he told the Observer last month.

All of Facebook’s 2.2 billion users will receive information entitled “Protecting Your Information”. This will be followed with a link to see what information has been shared with apps that they use.

The tech giant’s founder and CEO, Mark Zuckerberg, will testify before the US Congress on Tuesday.

The hearing is titled as “Facebook, Social Media Privacy, and the Use and Abuse of Data”. The second hearing, which is scheduled for April 11 is titled as, “Facebook: Transparency and Use of Consumer Data.”

Since the outbreak of the group’s scandal, the value in the group has plummeted. The social media giant has lost an estimated $80 billion in market value.