Apple today released Rapid Security Response (RSR) updates available to iPhone and iPad users who have iOS 16.4.1. This is the first quick security update that Apple releases to the public. Rapid Security Response Updates are designed to provide Apple users with security fixes without having to install a full system update.
Security updates are available through the software update mechanism in the iPhone or iPad settings application, but it is a quick update, requiring only two minutes to download the update and then a quick restart of the installation process.
What is Rapid Security Response (RSR) Update?
Apple launched this system of updates to mitigate some threats more quickly, especially those that have been exploited or reported to be in the public domain.
RSR updates can be installed automatically by default. Some of these updates can be installed without restarting the device, but some may require a restart. You can choose to turn off automatic installation of RSR updates through Settings, but that won't do you any good, because these updates provide important security improvements. So in order to protect your device, it might be best to let these updates install automatically.