在站点访问者的浏览器中检测Microsoft .NET Framework Assistant 1.2.1的存在

I need to detect if a user has the Microsoft .NET Framework Assistant 1.2.1 installed on their browser when they visit my site because I am making use of Microsoft's ClickOnce installer technology. This is a Firefox plugin. I've tried detecting it using navigator.plugins in JS but it's not coming back with anything useful. Is there some other way to detect the add-on's presence in a user's browser?I need to detect if a user has the Microsoft .N