Apple published on iOS 14.7.1 iPhones software update last month. The update fixed a security vulnerability that was allegedly exploited by hackers. After the release, the company stopped signing iOS 14.7. It means that iPhone users who have previously updated their device to iOS 14.7.1 will not be able to downgrade to iOS 14.7.
Apple often finishes signing legacy code after new iOS versions are released. This decision aims to protect users against malicious actors to exploit the vulnerabilities discovered. It also allows Apple to keep more devices on the latest versions of iOS.
As mentioned earlier, iOS 14.7.1 was released in July of this year. In addition to fixing the security vulnerability, the update also fixed a bug that prevented iPhones with Touch ID from unlocking a Apple watch. It was available for the iPhone 6s and later iPhones.
In the release notes for iOS 14.7.1, Apple stated that an app may be able to execute arbitrary code with kernel privileges. Claiming to be aware of a report that this issue may have been actively exploited, Apple has recommended all iPhone users to install the latest iOS update.