Even if your battery has been functioning normally, it may be worthwhile to update rather soon. Apple claims that iOS 15.4.1 (together with macOS Monterey 12.3.1, which was also published today) contains security fixes for vulnerabilities that might have been exploited in the wild. Unfortunately, this type of warning has become rather common in Apple’s security advisories — and while delaying upgrades forever has never been a good idea, it appears to be more critical than ever to ensure your devices are running the most recent version of their operating system.
