I don’t very often look at what has changed in macOS Security Updates, but in the case of Mojave 10.14.6 Security Update 2019-001, I thought it might be both interesting and useful for the many who haven’t yet orphaned all their 32-bit apps and upgraded to Catalina.

Apple’s release notes are as terse as they come: according to those, this update “improves the security of macOS”. And that’s it.

The accompanying security release notes refer to fixes in AppleGraphicsControl, Audio, CUPS, File Quarantine, File System Events, Graphics, IOGraphics, two kernel bugs, libxml2, libxslt, manpages, PluginKit, and UIFoundation.

Looking through the bundled apps, I was surprised to discover that Photos has been updated, its build number incremented to 3461.7.150, with accompanying new builds of its supporting frameworks and iCloud support.

Going a bit deeper, the following items in /System/Library have also changed significantly in this Security Update:

• several Assistant plugins
• Siri app, its version rising to 146.15.4
• Cloud Photos, with only a minor update
• AMD Radeon driver KEXTs, which here have minor increments rather than the more substantial version changes in macOS 10.15.1, but there’s no sign of any support for Radeon 6000 series graphics cards in Mojave
• Intel graphics driver KEXTs also have minor increments
• APFS rises from version and build number 945.275.7 to 945.275.8
• minor increments in many public and private frameworks
• Python framework rises from 2.7.10 to 2.7.16
• ‘Speech’ (Siri) preference pane is updated to version 146.15.4.

The overall build number for this new version of macOS Mojave is now 18G1012.

Included with this update, but not mentioned anywhere, are firmware updates for all models with T2 chips, which in this case brings their firmware version numbers into alignment with those of T2 Macs which have been upgraded to 10.15.1. However, models which lack the T2 chip don’t have any firmware updates on this occasion, which leaves them 1-3 versions behind the same model which has been upgraded to Catalina.

For those with multiple boot disks, providing the option of starting up in Catalina or an older version of macOS, this can cause confusion. Once a Mac has been upgraded to Catalina, it then runs the newer firmware installed in that upgrade even when it’s booted from the earlier version of macOS.

Unlike the 10.15.1 update, the Security Updates for High Sierra and Mojave don’t include the concurrent update to XProtect data files, which has to be downloaded and installed separately if you’re running an older version of macOS.