XProtect updates are available again
Apple’s software update servers are once again offering and providing updates to XProtect data for macOS Sonoma and earlier, as of about 0500 GMT today, 18 September 2024.
Software Update, the command tool softwareupdate, and SilentKnight should now be able to find XProtect version 5272, released on 28 August 2024, and install that for versions of macOS before Sequoia. I have verified this in both Sonoma and Monterey.
Although the update to version 5273 that was released on 16 September only for Sequoia 15.0 and later is still available, it remains unreliable. softwareupdate and SilentKnight report that both versions 5272 and 5273 are available, which is bizarre, and may then install either of them. If 5273 (or 5272) is installed into the local XProtect bundle, you can then get XProtect to ‘install’ it locally using the command sudo xprotect update. You may then end up with either version 5272 or 5273.
If you experience any difficulties with updating XProtect, please contact Apple Support so that they can report this within Apple.
Thanks to Joe for reporting this.