I am trying to follow the guide OAuth with Plugins | Plugin API but I got stuck on point 3.

3. This plugin iframe redirects to a hostname under your control, for example a page hosted on your internet server. This will place the iframe on a non-null origin, which enables us to securely check its identity later in the flow.

After opening an iFrame for authorization the origin is still null.

    figma.showUI(

      `<script>

        window.location.href = "https://myAuthProvider";

        console.log(window.origin); //null

      </script>`,

      { height: 600, width: 400 }

    );