From fcvl.net
OVERVIEW
On MacOS X version <= 10.14.5 (at time of writing) it is possible to easily bypass Gatekeeper in order to execute untrusted code without any warning or user’s explicit permission.
Gatekeeper is a mechanism developed by Apple and included in MacOS X since 2012 that enforces code signing and verifies downloaded applications before allowing them to run.
For example, if a user donwloads an application from internet and executes it, Gatekeeper will prevent it from running without user’s consens.