From https://www.virtualbox.org/wiki/Downloads, which is slow as molasses. Go there to get the checksums (you can't trust them from here).

VirtualBox 5.0.16 Oracle VM VirtualBox Extension Pack All supported platforms Support for USB 2.0 and USB 3.0 devices, VirtualBox RDP and PXE boot for Intel cards. See this chapter from the User Manual for an introduction to this Extension Pack. The Extension Pack binaries are released under the VirtualBox Personal Use and Evaluation License (PUEL). Please install the extension pack with the same version as your installed version of VirtualBox! See the changelog for what has changed. You might want to compare the

SHA256 checksums or the
MD5 checksums 

to verify the integrity of downloaded packages. The SHA256 checksums should be favored as the MD5 algorithm must be treated as insecure!