A single misconfigured proxy can quietly expose an entire internal network without breaking a firewall. In this video, we break down how HTTP/1 CONNECT evolved into HTTP/2 tunneling, why multiplexing makes it more powerful, and how a simple proxy configuration mistake can allow attackers to scan internal systems, access databases, and reach restricted services from the outside. We also look at real-world proxy setups like Apache and Envoy, and show how one or two incorrect settings can turn a security tool into an open tunnel. Finally, we cover practical fixes including strict allow-lists, authentication, and better monitoring.