I have once worked for a customer where other freelancer had developed a special proxy. The customer required working in a hermetically closed vpn environment even to access the test systems. Whitelisting a single web page cost an unreasonable amount of budget and took days to weeks. Therefore someone had decided to run the vpn inside a virtual machine, and developed an http proxy that consisted of two processes, one running inside the VM and one outside. Now, you gan guess how they exchanged requests and responses. That whole setup was surprisingly usable.