How can I get the contents of an iframe on a page using the firefox extension?

Question

Mozilla Firefox

Read elements in iframes located on other domains.
I know that browsers enforce cross-domain security policies, but many plugins, like firebug and other html inspectors, can access the content of a page's iframes. How do they do it. And is it possible to achieve this yourself?

Answer 1

This is not possible with JS. Only by proxying data through your domain.
And extensions have completely different capabilities and access rights than JS on the site.

Answer 2

Easily. Grab the Addon SDK and use Page-Mod. Just look at the dock all the settings Page-Mod'a. Content scripts are inserted into the desired frame, and then the standard communication with the background script of the extension is screwed on. Everything is described in the Addon SDK dock.