Wired
Apple released iOS 12.5.5 on September 24th, Japan time. This version is for models that do not support iOS 15, and users using iPhone 6s or later models are recommended to update to iOS 15.
Security update
Apple hasn’t announced any new features in iOS 12.5.5 (probably no new features). On the other hand, the release notes explain that it addresses multiple vulnerabilities. It has been confirmed that a malicious program using this vulnerability has been executed, and users of iOS 12 need to update immediately.
The compatible models of iOS 12 are iPhone5s, iPhone6, iPhone6 Plus, iPod touch6, the first iPad Air, iPad mini2, and iPad mini3. Even though it is an old model, there are many cases where it is used for children at home, for playing music, and still in active use. Even such models may be exposed to security risks as long as they are connected to the Internet, so they need to be updated.
The update can be done by going to “General”-> “Software Update” from the Settings app, which is the same as the normal update operation.
Source: MacRumors
(KAZ)
Source: iPhone Mania