How do Plugins/Flash Runtime work on IE

Question

How does any PlugIn work on a web browser ?

In which language is the Flash run time programmed ?

The PlugIns are a part of IE or any web browser, why can't they make system calls ? Are they not security threats ?

Answer 1

They use C++, of course.

Building Browser Helper Objects with Visual Studio 2005 : This article relies on Microsoft Visual Studio 2005 and Active Template Library (ATL) to develop a BHO using C++. We decided to use ATL because it conveniently implements a basic boilerplate that we can extend for our needs. There are other ways to create a BHO, such as using Microsoft Foundation Classes (MFC) or the Win32 API and COM, but ATL is a lightweight library that automatically handles a lot of the details for us, including setting up the registry with the BHO class identifier (CLSID).