A senator's open letter making it public that iPhone push notifications can be used to track users has let Apple publish a warning about the topic.
On Wednesday, Senator Wyden made a seemingly wild accusation that governments could use push notifications on iPhones and Android to spy on people. Apple immediately revealed that not only is this true, but also that the government had mandated that it not be revealed.
As well as publicly backing Wyden's call for both it and Google to be allowed to inform users of push notification issues, Apple has now added a warning to its "Legal Process Guidelines" document on the Apple website.
"When users allow an application they have installed to receive push notifications, an Apple Push Notification Service (APNs) token is generated and registered to that developer and device," says Apple under the new heading, "Apple Push Notification Service (APNs)."
"Some apps may have multiple APNs tokens for one account on one device to differentiate between messages and multi-media," it continues. "The Apple ID associated with a registered APNs token may be obtained with a subpoena or greater legal process."
It's still not known how common it is for requests for push notification data to be made by governments.