Tim Cook once scolded Travis Kalanick about Uber’s practice of tracking users even after they deleted the app from their iPhones. But in its newest operating system, iOS 11, Apple is rolling out a feature that will allow the same type of tracking—but with fewer privacy implications.

Apple’s new feature is called DeviceCheck and, if developers choose to use it, it will allow them to fingerprint and persistently track users’ iPhones, even if a user deletes the app or wipes their phone completely, using Apple as an intermediary.

To be clear, this kind of fingerprinting does not allow for location tracking. It lets developers keep track of former users’ devices so that, if they ever come back to the app, the developers will know they’ve been there before.

Source: Apple Rolls Out New Feature That Permanently Associates Devices with Apps, Even After Deletion

So what happens if you buy a second hand iphone?