Apple today released a second supplemental update for macOS Mojave 10.14.6, the current release version of macOS that's available to the public.
The macOS Mojave 10.14.6 Supplemental Update can be downloaded by going to the "Software Update" section of System Preferences and selecting the Update Now option. There are also updates available for macOS Sierra and macOS High Sierra.
There's little detail on what's included in today's update, but Apple's release notes say that it "improves the security of macOS" and is recommended for all users. According to a support document, it addresses a vulnerability that could allow remote attacker to "cause unexpected application termination or arbitrary code execution."
The next-generation version of macOS, macOS Catalina, is still in beta testing and is set to see a public release sometime in October, though Apple has not specified when.
Top Rated Comments
I recommend backing up all your data (separately, not as part of a Time Machine backup), formatting the drive down to bare metal/silicon, and doing a fresh from-scratch installation, then restoring your data. This should clean up whatever is hosed on the system that is causing updates to break it.