There is only one file type that uses the .VBOX extension:
Oracle VM VirtualBox Settings File
A VBOX file is a settings file used by Oracle VM VirtualBox, a program used for running virtualized operating systems (OSs). It is saved in an XML format and contains settings such as the virtual machine name, OS type, system memory. VBOX files are used for launching virtual machines (VM).
By default, VBOX files are saved in a directory with the disk images they reference (.VDI files). The filename prefix of both the VDI and VBOX files is the VM name set by the user when the VM was created (e.g., Windows 7.vbox and Windows 7.vdi).
NOTE: The VBOX extension was introduced with Oracle VM VirtualBox version 4.0. Older versions of the software saved settings in a file called VirtualBox.xml.
Updated: December 15, 2017