If you use both WhatsApp and Facebook, this change allows Facebook access to several pieces of your WhatsApp information, including your WhatsApp phone number, contact list, and usage data (e.g. when you last used WhatsApp, what device you used it on, and what OS you ran it on). With confusing wording, the update correctly points out that your phone number and messages will not be shared onto Facebook. This means that your data will not be shared publicly on your Facebook page or anywhere else on Facebook’s platform. Instead, it will be shared with Facebook—that is, Facebook systems and the “Facebook family of companies.” While WhatsApp’s privacy-friendly end-to-end encryption remains, and the company assures users it will not share their data directly with advertisers, this nevertheless presents a clear threat to users’ control of how their WhatsApp data is shared and used.

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Most critically for user privacy, however, sharing this kind of metadata also gives Facebook an enhanced view of users’ online communication activities, affiliations, and habits, and runs the risk of making private WhatsApp contacts into more public Facebook connections. The new privacy policy, for example, permits Facebook to suggest WhatsApp contacts as Facebook friends. Facebook can also use the data to show “more relevant” ads. In an announcement accompanying the privacy policy update, WhatsApp offers the example of “an ad from a company you already work with, rather than one from someone you’ve never heard of”—a frightening prospect considering the data coordination and sharing required for Facebook to know the companies with whom you do business.