Earlier today, JatoBZ, an iOS reverse engineer tweeted a photo of an iPhone 5S which had the iOS 10.3.3 update available through settings, showing that iOS 10.3.3 is still signed for the device. Usually, only the latest iOS builds are signed by Apple, but in some cases, other versions are still signed for some devices due to various reasons. This holds true in the case of the iPhone 5S, and likely other A7-powered devices, as iOS 10.3.3 is still signed. Signing is the process which Apple uses to indicate which iOS versions iTunes will allow you to restore to. If an iOS version is not signed by Apple, you cannot downgrade or upgrade to it, as iTunes will show an error. In this case with iOS 10.3.3 still signed, it should mean that you can downgrade or upgrade to it with iTunes, in the event that a jailbreak is released for it. This is where downgrades are especially useful when you can restore down to a jailbreakable iOS version. Supposedly, iPhone 5S and other A7-based devices have issues directly updating from iOS 7 to iOS 11. In which case, before updating to iOS 11, you have to update to iOS 10.X.X first, in order to upgrade which led Apple to keep signing the latest available iOS 10 version for these devices. This should be great news for iOS jailbreakers who have older devices and are holding out hope for an iOS 10.3.X jailbreak. Currently, the latest available jailbreak for 64-bit devices is only compatible up to iOS 10.2.1. Any versions newer than that cannot currently be jailbroken, but this news means that if one is released for iOS 10.3.3, 5s owners should be able to downgrade and jailbreak their devices.