In a nutshell:
document.formId.action = "http://third.party.service.com/script.php";
document.formId.inputName.value = "some value";
document.formId.submit(); // submit form
You can access the
document of an iframe:
var iframedoc = document.getElementById('the_iframe').contentWindow.document;
var inputs = iframedoc.getElementsByTagName('input');
// do stuff with inputs...
iframedoc.getElementsByTagName('form').submit(); // submit a form
I've never actually done this so I'm not sure if it'll work - I suspect not because of this:
Hey guys couldn't use that method, seems its cross site scripting so I had to use the GET method.