I'm new to cybersecurity, but I always knew some basic things, or at least I thought so, until I found out that the Flash app may actually get my real IP address even if I'm behind elite proxy. How does Flash find out the real IP? What is the technique for this and is it possible to secure myself from it without disabling Flash? How can I check if I am in fact vulnerable to this?
It's because flash doesn't actually care for your proxy preferences. You can change that in your flash player settings, but even then, flash applications can choose to try to connect directly and ignore your proxy settings. A proxy is nothing more than a "suggestion" to a program. It is up to the programs to actually follow those settings, or ignore them. A webbrowser doing HTTP by itself will probably honor your proxy settings, but technologies outside, or "next to" the browser (like plugins and WebRTC) may simply do whatever it wants.