Correction: I assumed it was iTunes that was being updated, because a pop-up asked me to close it.
From the log, it was a new version of Safari:
PKLeopardPackage <id=com.apple.pkg.Safari13.0MojaveAuto, version=1.0.0.0.1.1567552241, url=file:///Library/Updates/041-98185/Safari13.0MojaveAuto.pkg
the install log shows a few other packages seemed to fail:
"PKLeopardPackage <id=com.apple.pkg.MobileDeviceOnDemand.1300A38, version=1.0.0.0.1.1567124787, url=file:///Library/Updates/041-43993/MobileDeviceOnDemand.pkg>",
"PKLeopardPackage <id=com.apple.pkg.CoreTypes.1300A38, version=1.0.0.0.1.1567124787, url=file:///Library/Updates/041-43993/CoreTypes.pkg>"
)
2019-09-21 07:38:00+10 sooty system_installd[733]: Package Authoring Error: PackageInfo bundle reference found without top-level bundle definition. Bundle will be skipped: <bundle id="*"></bundle>
2019-09-21 07:38:00+10 sooty system_installd[733]: Package Authoring Error: PackageInfo bundle reference found without top-level bundle definition. Bundle will be skipped: <bundle id="*"></bundle>
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Bundle com.apple.SyncServices.AppleMobileDeviceHelper is nested inside upgrade-bundle or atomic-update-bundle and will not be version-checked
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Bundle com.apple.SyncServices.AppleMobileSync is nested inside upgrade-bundle or atomic-update-bundle and will not be version-checked
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Bundle com.apple.MobileDeviceUpdater is nested inside upgrade-bundle or atomic-update-bundle and will not be version-checked
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Bundle com.apple.MDRemoteServiceSupport is nested inside upgrade-bundle or atomic-update-bundle and will not be version-checked
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Skipping component "com.apple.macos.driver.AppleUSBEthernetHost" (7.0.0-7.0.0-152000000000000) because the version 8.1.1-8.1.1-144200002000000 is already installed at /System/Library/Extensions/AppleUSBEthernetHost.kext.
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Skipping component "com.apple.DeviceLinkX" (5.0.0-264.0.0-276000000000000) because the version 5.0.0-264.0.0-1311000000000000 is already installed at /System/Library/PrivateFrameworks/DeviceLink.framework.
2019-09-21 07:38:00+10 sooty system_installd[733]: PackageKit: Extracting file:///Library/Updates/041-43993/MobileDeviceOnDemand.pkg (destination=/.PKInstallSandboxManager-SystemSoftware/F435D994-708C-4B38-86FC-BA643BE3AB81.activeSandbox/Root, uid=0)
2019-09-21 07:38:01+10 sooty system_installd[733]: PackageKit: Extracting file:///Library/Updates/041-43993/CoreTypes.pkg (destination=/.PKInstallSandboxManager-SystemSoftware/F435D994-708C-4B38-86FC-BA643BE3AB81.activeSandbox/Root, uid=0)
2019-09-21 07:38:03+10 sooty system_installd[733]: PackageKit: xpchelper --rebuild-cache --overlay /.PKInstallSandboxManager-SystemSoftware/F435D994-708C-4B38-86FC-BA643BE3AB81.activeSandbox/Root
2019-09-21 07:38:09+10 sooty system_installd[733]: PackageKit: prevent user idle system sleep
2019-09-21 07:38:09+10 sooty system_installd[733]: PackageKit: suspending backupd
2019-09-21 07:38:09+10 sooty system_installd[733]: PackageKit: Executing script "preinstall" in /private/tmp/PKInstallSandbox.JkbJ84/Scripts/com.apple.pkg.MobileDeviceOnDemand.1300A38.h96gtu
2019-09-21 07:38:09+10 sooty colin[5849]: Running Install Scripts . . .
2019-09-21 07:38:09+10 sooty install_monitor[5846]: Temporarily excluding: /Applications, /Library, /System, /bin, /private, /sbin, /usr
2019-09-21 07:38:09+10 sooty colin[5851]: Begin script: usbmuxdpre
2019-09-21 07:38:09+10 sooty system_installd[733]: preinstall: /System/Library/LaunchDaemons/com.apple.usbmuxd.plist: Operation not permitted while System Integrity Protection is engaged
2019-09-21 07:38:09+10 sooty system_installd[733]: preinstall: (kernel) Kext com.apple.driver.AppleMobileDevice not found for unload request.
2019-09-21 07:38:09+10 sooty system_installd[733]: preinstall: Failed to unload com.apple.driver.AppleMobileDevice - (libkern/kext) not found.
2019-09-21 07:38:09+10 sooty system_installd[733]: preinstall: (kernel) Kext com.apple.macos.driver.AppleUSBEthernetHost not found for unload request.
2019-09-21 07:38:09+10 sooty system_installd[733]: preinstall: Failed to unload com.apple.macos.driver.AppleUSBEthernetHost - (libkern/kext) not found.
2019-09-21 07:38:09+10 sooty colin[5857]: End script: usbmuxdpre