This morning, Amazon announced that it has released a "mandatory" update to its Kindle app on iOS. Kindle users on iOS received the notification informing them that failure to update the app to the latest version could cause the loss of books and account registration when upgrading to Apple's new iOS 7 mobile operating system.
It is widely expected that iOS 7 will be released tomorrow during Apple's launch event, at which it will also debut the new iPhone 5S and iPhone 5C, of which both devices are said to be running iOS7 out of the box. There is no explanation as to why books may be lost without the update, but since it's free and only takes a few minutes, upgrading to the new version should not be an issue for any user.
The warning notification users received is below:
This is a fix for a Kindle issue with the upcoming iOS7 OS upgrade that may cause customers to have to re-register and re-download books from Amazon. Please download and install - this is a required update before upgrading to iOS7.