According to Apple’s release notes for the Catalina 10.15.3 update, there are only two changes which merit specific mention:
- optimisation of gamma handling for the Pro Display XDR,
- improvement in video editing performance in HEVC and H.264 4K video on the latest MacBook Pro 16-inch.
Almost every model also had an EFI firmware update, which has finally brought all models running supported versions of macOS (10.13-10.15) into alignment. So now it doesn’t matter which version of macOS your Mac is running, from High Sierra to Mojave, its firmware version should remain the same (although different models still use different versions).
Security fixes include updating PHP to version 7.3.11, a Gatekeeper bypass from an NFS mount, two remote Bluetooth attacks, vulnerability to crafted JPEG images, five kernel bugs, validation of symlinks in packages, and a remote Wi-Fi attack. Apple provides detailed security notes here.
Bundled apps which have undergone significant change between 10.15.2 and 10.15.3 include:
- Bluetooth File Exchange, new version 7.0.3 replaces 7.0.2
- Boot Camp Assistant, minor update to build 6170.80.4
- Dictionary, minor update to build 239.1.1
- Mail, substantial update to build 3608.60.0.2.5
- Music, new version 1.0.3 replaces 1.0.2
- News, new version 5.3.1 replaces 5.3
- Photos, substantial update to build 131.17.170
- TV, new version 1.0.3 replaces 1.0.2
- VoiceOver Utility, minor update to build 708.5.7.
Supporting components have also undergone quite widespread change. Among the most prominent are:
- Accessibility, minor updates in build numbers across most components
- AirPlay audio plug-in and others, minor update in build number
- Bluetooth Setup Assistant, new version 7.0.3 replaces 7.0.2
- Spotlight, minor update to build 2075.7
- VoiceOver app, minor update to build 708.5.7
- Many graphics driver extensions, including substantial updates to most AMD support, to version 3.5.5, and Apple Intel support, to version 14.4.23
- Apple Storage Drivers, updated to new version 489.80.2
- Bluetooth driver, updated to version 7.0.3
- Thunderbolt drivers, updated to new versions
- APFS, updated from 1412.61.1 to 1412.81.1
- SMBFS, updated from 3.4 to 3.4.1
- Bluetooth preference pane, from version 7.0.2 to 7.0.3
- Private frameworks, including AirPlay and Mail
- Braille drivers have been updated.
Standalone updaters are available as follows:
- 10.15.3 ‘delta’ (incremental) update
- 10.15.3 Combo update [NOTE: Apple has now corrected this on the US page at the link given here, but this may take longer to propagate out to other locales].
- Mojave Security Update 2020-001
- High Sierra Security Update 2020-001.
Sierra has been unsupported since the release of Catalina last October, and now receives no security updates or firmware updates.