Apple blocks signatures for iOS 8.4

Apple has just closed the signatures for iOS 8.4 on all models of iPhone, iPod and iPad compatible with this version of the operating system. Now you can then only restore to iOS 8.4.1.

If you use an iPhone, iPod or iPad with iOS 8.4, now you can not go back to this version of the software if you perform a restore, because the only remaining version is 8.4.1. This also means that, if you have upgraded to iPhone OS 8.4.1, you can not downgrade to a previous version.