MacStadium offers older versions of macOS1 for customers desiring to access that operating system version on a bare metal hosted Mac.
Our policy is we rent the hardware and install the OS of the renter's choice from the operating systems available to run on the hardware we host. We have customers with hosted and colocated machines of various operating systems.
We have no way of knowing which OS any one user has installed after release of the server unless we are granted access by the user to troubleshoot or modify the server's configuration. Once a customer has accessed a server, it is their responsibility to maintain the software on the device and to be aware of security vulnerabilities related to running older operating systems.
Customers running ESXi are able to run any OS under virtualization. We make a reasonable attempt to monitor our network (while maintaining the privacy of our customers) and protect the integrity of said network as its health is of paramount concern to the experience of our customers.
It is the customer's responsibility to secure their machine in accordance with our Terms of Service. Failure to do so will result in termination of services.
As a company policy, we make a reasonable attempt to keep our customer's informed of known security vulnerabilities on our blog.
1. macOS may be interchangeable with OS X, the name used for previous versions of Apple's Mac operating system. ↩