Facebook will begin notifying the 87-million users affected by the Cambridge Analytica scandal on Monday.

Cambridge Analytica is a London-based political consulting firm that gathered private data on millions of unaware Facebook users.

This collection was considered legal by the rules that Facebook had in place at the time.

Those who may have had their private information shared by the data mining company will get a detailed message on their news feeds.

Facebook says 620,000 Canadian users were affected.

According to Facebook CEO Mark Zuckerberg, the 87-million users figure is an estimated number.

Cambridge Analytica whistleblower Christopher Wylie says the true number could be even higher.

All 2.2-billion Facebook users will receive a notice titled, “Protecting Your Information” with a link to see what information has been shared.