If you’re still running Big Sur or Catalina and have been puzzled as to why their recent security updates didn’t include Safari 15.2, then the mystery is solved: Apple has just released a separate update which brings Safari in macOS 11.6.2 and 10.15 to version 15.2, matching that in Monterey 12.1. This should be available through Software Update or
Although this is also likely to be discovered by SilentKnight, as it’s a more substantial update than the usual small security data updates that app is intended for, I recommend that you use Software Update to download and install it.
Most importantly, this update brings a batch of security fixes, detailed here.
Separate Safari updates are possible in Big Sur and Monterey because Safari itself isn’t installed on the signed and sealed System volume, so can be installed without recreating the boot snapshot. This update also has a different build number from that in Monterey.
Thanks to Mr. Macintosh for drawing attention to this.