Major mobile apps from companies including Yelp and Duolingo send data that could be used personally identify you for ad tracking straight to immediately upon logging in, according to a new report from the London-based UK charity and watchdog group Privacy International (PI).

from https://www.theverge.com/2019/3/5/18252397/facebook-android-apps-sending-data-user-privacy-developer-tools-violation
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