Virtualbox is a godsend for developers looking to run multiple operating systems from within the same computer but if you try installing that software on MacOS Mojave you might experience the following error:
Thankfully fixing that is relatively quick and easy.
Quit the VirtualBox installer and open up your Mac's System Preferences (either from the link in the Apple menu at the top left of the screen or, if you have the System Preferences icon displayed in your system dock, from the dock instead):
Once loaded simply click on the Security & Privacy icon which should then display the following screen:
Notice the message informing you that System software from developer "Oracle America, Inc" was blocked from loading?
This is thanks to Mac's in-built security software called GateKeeper which disallows untrusted applications from being able to be installed.
Simply click on the Allow button (as displayed in the above screen capture) to remove this restriction for the VirtualBox software.
Now relaunch the VirtualBox installer and you should find the software is now able to be successfully installed like so: