Oz was originally created and submitted to HackTheBox. It is a medium/hard boot2root challenge. The Oz box has 2 flags to find (user and root) and has a direct route for each, no need to bruteforce access. It is a slightly trolly box with real world vulnerabilities. The OVF has been tested on VirtualBox, VMware Fusion, and VMware Workstation.
If you have questions or concerns we can be contacted via Twitter - @incidrthreat and @ilove2pwn_