Server Side Request Forgery
Server Side Request Forgery (SSRF) is an attack that allows an attacker to make requests from a vulnerable server (web site) to the internal network (Intranet). It is not possible to send a direct request to the internal network of the attacked infrastructure from outside.
Service A (anonymous-proxy.com) provides the functionality of an anonymizing proxy server. On web site there is a form for entering URL. Web site reads the contents of the requested URL and displays the response to a user.