ABSTRACT
Most Web browsers have a standard behavior of listening on port 80 for HTTP traffic and port 443 for HTTPS traffic. A Web server is only supposed to access files reachable from its own document root directory. But the common gateway interface (CGI) is intended to allow ordinary programs (those that are not Web servers) to interact using a Web browser interface. Ordinary programs are not bound by the same rules as a Web server, and they can access any part of the file system. CGI interfaces are present at the core of almost all Web applications.
