I have been waiting for these to drop as parallel to the released recently Catalina 10.15.7 Supplemental Update to build 19H15 and iOS 14.2 updates (and was surprised nothing happened within a week of that release since they patched active zerodays):
As of Thursday 2020-11-19 12:30GMT there is a new KB https://support.apple.com/kb/DL2062 and I'm including the direct download link for Mojave Security Update 2020-006 (build 18G6042) here: https://updates.cdn-apple.com/2020/macos/001-72535-20201103-4257080a-b809-41ac-9924-6e5d7ce73963/Sec...
I won't be looking for High Sierra - a direct download link has yet to be posted so the only way you can get this likely final security update for High Sierra is through Software Update - but thought having a thread might help others. ( hint @ClassicII must be taking a little much deserved time off after publishing a lot of details about Big Sur.)
In my org we have a number of systems we can't run Apple Software Update on (isolated networks) and we've found a combination of pushing policies to cache, inventory (so that the cached item populates a smart group), run a command line to check version and if not updated run the policy trigger for install cache (because the updater will reboot and not register the policy's run) but that only works for most of the Macs in this category most of the time; we also have to periodically push a second straight up complicated install script to run the installer on the rest (about 20% of the total.)
Warning - at the moment it looks like the SSL cert for cdn-apple.com is expired! You may need to do run something like this:
curl -C - -k "https://updates.cdn-apple.com/2020/macos/001-72535-20201103-4257080a-b809-41ac-9924-6e5d7ce73963/SecUpd2020-006Mojave.dmg" -O
As of Tuesday 2020-11-17 12:07GMT no download link has yet been posted (I checked all possible links https://support.apple.com/kb/DL20[55-80] none were for 2020-006 for Mojave or High Sierra.)