Some people out there may not know that each iPad and iPhone on the market has a special identification number known as a UDID. For a long time there've been a number of apps on the App Store that access that unique identification number. Presumably, by using that number a developer would be able to tell when a specific iPad the downloaded an app.
With significantly increasing pressure from Congress in the United States over privacy, Apple has decided to step up its privacy game without prompting from Washington. Apple has started rejecting any app that accesses the UDID. Apple had reportedly already notified developers that they only have six months left ago before the UDID was depreciated.
TechCrunch reports that some larger social media mobile app developers told it previously that Apple is reaching out and warning them to move away from the UDID earlier than expected. Apple is now simply rejecting apps that access that identification number. Apparently mobile ad networks, game networks, analytic services, that testing systems all access the UDID on consumer devices. It's not clear what will happen to apps already on the app store that access the UDID.