Tracking UTL parameters through cookies

Has anyone come up with a solution to maintaining original UTM parameters so they are not lost if someone clicks through your site? I was thinking of trying my hand at using javascript to create a cookie with the original landing url and utm parameters for that url and then pass it to a Marketo form if/when the person fills out a form.

Has anyone already done this and be willing to share ideas/thoughts?

Secondary question would be what exactly does Marketo capture in Munchkin? Does it capture document.referrer or things like location.hostname, pathname, and search? I am getting a lot of leads with the original referrer being our site. All our pages have munchkin on them so shouldn't it be equal to the page before they landing on our site? (assuming it isn't direct)