It is the first thing you need to fix the issue as stated above. For that, you need to run the virtual machine showing the error and go to the Devices > Install Guest ...

How to install BackBox Linux distribution as a virtual machine Your email has been sent Several Linux distributions are available nowadays for security and penetration testing. BackBox Linux is one of ...

Oracle has released patches for ten vulnerabilities in VirtualBox which allow attackers to break out of guest operating systems and attack the host operating system that VirtualBox runs on. Exploits ...