A Russian internet company with links to the Kremlin could have had access to the Facebook data of millions of people in the US without their knowledge, CNN has learned.
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“What this means is that all data that Facebook users shared through this agreement with Mail.Ru is now available to the Russian intelligence services. All of it. And that is incredibly troubling,” Carpenter said.

Source: Russian company could have accessed Facebook data on millions of Americans, source says
We presume that U.S. intelligence agencies already had access. Of interest, Facebook is building out an enormous data center almost next door to the NSA’s huge Utah Data Center.
Facebook and mail.ru deny any collection of data. Facebook has, in the past, frequently denied direct and indirect data collection only to reveal later that data was collected by third parties.