Inject javascript into Firefox with easyhook possible?

May 19, 2009 at 12:24 PM

I'm trying to figure out how to inject javascript code into Firefox, and other browsers, when the user is browsing the internet. Does anyone here have an idea on how that could be done, or if it can be done at all? 

Firefox should be a good proof of concept since it is open-source and finding the proper entry-point should not prove to be too difficult.