mozilla-release/testing/web-platform/tests/upgrade-insecure-requests/link-upgrade/iframe-top-navigation-upgrade-1.sub.html

<html>
  <head>
    <title>Upgrade Insecure Requests: top-frame navigation inside iframe (upgrade expected)</title>
  </head>
  <body>
    <!--
    This is a bit of a hack. UPGRADE doesn't upgrade the port number, so we
    specify this non-existent URL ('http' over https port). If UPGRADE doesn't
    work, it won't load. The expected behavior is that the url is upgraded and
    the page loads.
    -->
    <iframe
      sandbox="allow-scripts allow-top-navigation"
      src="https://{{domains[www]}}:{{ports[https][0]}}/upgrade-insecure-requests/link-upgrade/resources/navigate-top-frame.sub.html?url=http://{{host}}:{{ports[https][0]}}/upgrade-insecure-requests/link-upgrade/resources/post-message-to-opener.sub.html%3Fmessage=iframe-top-navigation-upgrade-1"
    ></iframe>
  </body>
</html>