Apple has pushed an update to the data used by Gatekeeper, bringing its version number to 181, dated 26 August 2019. The last update had taken it to 179, and version 180 doesn’t appear to have been released.
Apple provides no details as to what changes this update brings, but it is normally expected to include recent revocations of security certificates used in signing software.
You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.
A full listing of security data file versions is given by SilentKnight,
silnite, LockRattler and SystHist for El Capitan, Sierra, High Sierra, Mojave and Catalina, available from their product page. If your Mac has not yet installed this update, you can force an update using SilentKnight, LockRattler, or at the command line.
I have updated the reference pages here which are accessed directly from LockRattler 4.2 and later using its Check blog button.