VirtualBox 5.1.28 fails to install on MacOS 10.13 due to KEXT security
Managed to solve it.


Eject the VirtualBox image from: Finder > Devices


Now allow the exception in: System Preferences > Security &amp; Privacy


Finally but not least click Allow button so that way the developer with the name "Oracle America, Inc" will be accepted and the installer using that certificate will run just fine (basically this installer is signed using "Oracle America, Inc" certificate so we are required to enable it use on our machine first)
Then try to install from the .dmg again so that it remounts the device.


Now its working fine for me.