There is a critical vulnerability in Safari that if exploited can result in arbitrary code execution with kernel privileges. All users should update as soon as possible.
For more information, please see the following:
macOS 12.5.1: https://support.apple.com/en-us/HT213413
iOS 15.6.1 and iPadOS 15.6.1: https://support.apple.com/en-us/HT213412
Safari 15.6.1 for macOS Big Sur and macOS Catalina: https://support.apple.com/en-us/HT213414
It is being reported that these vulnerabilities have been actively exploited. As ever we would recommend that macOS is configured to automatically install updates as per https://support.apple.com/en-gb/guide/mac-help/mchlpx1065/mac