VirtualBox Guest Additions provide closer integration between host and
guest, and improve the performance of guest systems.

Non-legacy additions i.e. emulators/virtualbox-ose-additions are
recommended for most use cases.

Where legacy (5.2.x) is a requirement, this FreeBSD-provided package
can be installed in the FreeBSD guest machine.

<https://www.virtualbox.org/wiki/Changelog-5.2> emphasises that
5.2.x is no longer supported by Oracle.

Additions are not intended for use on Host machines.

WWW: https://www.virtualbox.org/