Edit Iframe with chrome extension on nike page

Question

I am trying to make a chrome extension that checks out on nike (for purely experimental purposes of course) but I am having some trouble. Nike keeps its credit card forms in iframes which I can't edit.

I tried using all_frames but it doesn't work. I get the error "Blocked a frame with origin "https://www.nike.com" from accessing a frame with origin "https://paymentcc.nike.com". Protocols, domains, and ports must match." here is the code I use

setTimeout(function () {
  console.log("included")
  const iframe = document.getElementsByClassName("u-full-widthcss-k72947")[0]
  const iframeDocument = iframe.contentWindow.document;
  console.log(iframeDocument.body)
}, 10000)