OS 26.3.1(a) arrives as a background security update with a WebKit navigation API input-validation fix, with no new features expected.
OS 26.3.1A adds Background Security Improvements with a manual Install option in Settings > Privacy & Security, for iPhone ...
Apple has detailed the security content for iOS and iPadOS 16.7.15, 15.8.7, 16.7.15, and 15.8.7, confirming that they address ...