14 DAY TRIAL // Affecting mostly jailbreakers, but also those who wanted to downgrade from iOS 11.3, Apple has recently stopped signing the previous iOS 11.2.6 firmware prohibiting such operations.
If already updated your iPhone, iPad or iPod touch device to the latest iOS 11.3 release and now you plan on downgrading to iOS 11.2.6, it's no longer possible as Apple stopped signing the firmware, thus killing downgrades, but also prohibiting jailbreakers to release a custom firmware for its devices.
The same goes for those using earlier versions of iOS, before version 11.2.6, as they can now only update their devices to iOS 11.3, and can no longer downgrade to iOS 11.2.6 using iTunes. Of course, if you have already downloaded the iOS 11.2.6 firmware, it might be possible to downgrade manually, but it isn't recommended.
Apple forces iPhone, iPad and iPod users to upgrade to iOS 11.3
iOS 11.3 is now the latest and most advanced version of Apple's mobile operating system for supported iPhone, iPad, and iPod touch devices, adding the controversial Battery Health feature that lets users finally disable the deliberate performance slowdowns that the company implemented in earlier iOS releases.
Additionally, iOS 11.3 introduces new AR (Augmented Reality) experiences, Business Chat in Messages to better communicate with your local businesses, a new Health Records feature in the Health app as a central hub of your health data, four new Animoji for iPhone X users, and much more.
The company regularly stops signing previous iOS versions shortly after a new release is available, thus forcing users to use the latest release either by not allowing them to downgrade to a previous build or upgrade directly to the latest one. We believe this is a good move in order to maintain a healthy iOS ecosystem.
We recommend all iPhone, iPad, and iPod touch users to upgrade to iOS 11.3 as soon as possible if they didn't do so already, as not only they'll probably get battery life and likely a performance boost, but also several new features to make their mobile experience more enjoyable and secure.