iPhone apps share data with trackers, ad companies and research firms

Other trackers pay the app makers, squeezing value out of our data to target ads. Three more trackers help DoorDash monitor app performance — including one called Segment that routes onward data including your delivery address, name, email and cell carrier. Apple offers a privacy setting called “Limit Ad Tracking” (sadly off by default) which makes it a little bit harder for companies to track you across apps, by way of a unique identifier for every iPhone.

Source: www.washingtonpost.com