Mike Schroepfer, Facebook's chief technology officer, dropped a bombshell yesterday: Facebook might have "improperly shared" the data of up to 87 million people with Cambridge Analytica, the U.K.-based political consulting firm that worked for President Donald Trump's 2016 election campaign. Schroepfer made the comment at the end of a lengthy post about the company's new measures to protect users' personal information.

Among those whose information was exposed to the consultancy, 81.6 percent -- more than 70.6 million -- were users in the U.S. Other countries whose residents' data ended up in Cambridge Analytica's hands included the Philippines (nearly 1.2 million), Indonesia (more than 1 million), the U.K. (over 1 million), and Mexico (close to 790,000).

Cambridge Analytica had already been widely recognized for its role in promoting Trump's presidential campaign. However, several recent reports have revealed the extent to which the firm used the data of Facebook users without their knowledge to aim targeted ads and messages at likely Trump voters. Those reports have dramatically turned up the political and public opinion heat on Facebook CEO Mark Zuckerberg, who is scheduled to testify before multiple congressional committees next week.

Facebook To Tell People If Info Improperly Shared

Since dismissing criticisms about Facebook's role in manipulating voters as "crazy" in late 2016, Zuckerberg has repeatedly been forced to acknowledge the extent to which the social media platform has enabled "digital warfare" through the vast amounts of data it gathers, stores, and shares about its users. Over the past month, news reports about improper data usage have led the company to announce a number of new policies, including changes to make privacy tools easier to use and new limitations on information shared with third-party apps and data brokers.

In his news post yesterday, Schroepfer listed nine other changes the company plans to make in the coming months. They include greater restrictions on user data shared with third-party apps via Facebook's Events, Groups, and Pages APIs (application programming interfaces); an end to a feature enabling searches for Facebook users via phone numbers or email addresses; and new limits on the data collected about the call and text histories of mobile users.

Starting Monday, Facebook will also provide a link at the top of users' News Feeds to show them what apps they are using and what personal data is shared with those apps, Schroepfer added.

"As part of this process we will also tell people if their information may have been improperly shared with Cambridge Analytica," Schroepfer wrote. "In total, we believe the Facebook information of up to 87 million people -- mostly in the US -- may have been improperly shared with Cambridge Analytica."

House and Senate Hearings, Australian Investigation

On Tuesday, Zuckerberg is set to appear as the only witness during a joint hearing of the Senate Judiciary Committee and Senate Commerce, Science, and Transportation Committee. The following day, he's scheduled to testify before the House Energy and Commerce Committee.

"Our joint hearing will be a public conversation with the CEO of this powerful and influential company about his vision for addressing problems that have generated significant concern about Facebook's role in our democracy, bad actors using the platform, and user privacy," Commerce Committee Chairman John Thune (R, South Dakota) said in a statement.

In a joint statement, Energy and Commerce Committee Chairman Greg Walden (R, Oregon) and ranking committee member Frank Pallone Jr. (D, New Jersey) added that Wednesday's hearing will provide "an important opportunity to shed light on critical consumer data privacy issues and help all Americans better understand what happens to their personal information online."

Today, Angelene Falk, Australia's acting privacy commissioner and Australian information commissioner, said her office was opening a formal investigation into Facebook. More than 311,000 Australians had their Facebook information improperly shared with Cambridge Analytica, according to the data provided yesterday by Schroepfer.

"The investigation will consider whether Facebook has breached the Privacy Act 1988 (Privacy Act)," Falk said in a statement. "Given the global nature of this matter, the [Office of the Australian Information Commissioner] will confer with regulatory authorities internationally."