Target and alter <iframe> contents from another domain
I've had a good look around and I'm getting the impression that this isn't possible.
I want to add some classes to various bits on one of Worldpay's lovely :goof: payment iframes so I can make it look something like the site it's sat on.
This is the original principle I was using, which works when on a page with the same domain.
$(this.contentDocument).find('body').html('Test: This frame was modified with js')