Geoffrey A. Fowler, Washington Post:

On a recent Monday night, a dozen marketing companies, research firms and other personal data guzzlers got reports from my iPhone. At 11:43 p.m., a company called Amplitude learned my phone number, email and exact location. At 3:58 a.m., another called Appboy got a digital fingerprint of my phone. At 6:25 a.m., a tracker called Demdex received a way to identify my phone and sent back a list of other trackers to pair up with.

And all night long, there was some startling behavior by a household name: Yelp. It was receiving a message that included my IP address -— once every five minutes.

And:

You might assume you can count on Apple to sweat all the privacy details. After all, it touted in a recent ad, “What happens on your iPhone stays on your iPhone.” My investigation suggests otherwise.

iPhone apps I discovered tracking me by passing information to third parties — just while I was asleep — include Microsoft OneDrive, Intuit’s Mint, Nike, Spotify, The Washington Post and IBM’s the Weather Channel. One app, the crime-alert service Citizen, shared personally identifiable information in violation of its published privacy policy.

This is a big deal. Privacy is core to Apple’s brand and one of the main reasons I am so loyal to Apple’s ecosystem. Looking forward to Apple’s response to the Washington Post.