Shortnote

Back in the days, ActionScript was designed to provide "beautiful" website graphics, later it started streaming movies and now it is turning into a fully-blown Object Oriented Programming Language that has access to your hardware and can thus read your network details. The API on Adobe lists the function InterfaceAddress and is available online.

Mitigations

Delete all Flash plugins (and live in the middle-ages of the Internet).
Use a VM.