Apple has today pushed another update to its Gatekeeper configuration data, bringing it to version 129. As usual, Apple does not announce this, nor reveal what the update does.
I have today posted a new version of my popular free tool LockRattler, which checks and shows version numbers of currently-installed security configuration data, including that for Gatekeeper. This version, 3.5, should at last run on El Capitan and High Sierra, as well as on Sierra. It is available from here.