Apple has stopped signing iOS 12.3.1 and 12.3.2 after the release of iOS 12.4. That means that it’s no longer possible to downgrade again from the latest version of iOS if you’ve already upgraded.
For at least one big reason, that’s a very good thing.
iOS 12.4 arrived on July 22. It introduced enhancements to Apple News+, superior iPhone migration tech, and more. The most important change, however, were fixes to several security flaws. These were discovered by Google’s Project Zero team. They allowed a hacker to run malicious code on an iPhone via an iMessage exploit.
All that would need to happen for a code to be launched is for a recipient to read one of the tainted messages. (Google has discovered the existence of one other iMessage flaw, although it’s keeping it under wraps since Apple has not yet fixed it.)
iOS 12.4 will be one of the last major releases for iOS 12 before Apple introduces iOS 13 in September.
Apple frequently stops signing older versions of its software to push as many users as possible to run the latest versions. By sprinkling iOS upgrades with a combination of visible new features with under-the-hood improvements, it prompts users to upgrade. The upgrade numbers speak for themselves. When Apple last published iOS 12 figures on its developer webpage in May, 87% of all devices introduced in the last 4 years were using some version of iOS 12.
