{
  // see https://bugzilla.mozilla.org/show_bug.cgi?id=1415644
  let domains = [
  "accounts-static.cdn.mozilla.net",
  "accounts.firefox.com",
  "addons.cdn.mozilla.net",
  "addons.mozilla.org",
  "api.accounts.firefox.com",
  "content.cdn.mozilla.net",
  "content.cdn.mozilla.net",
  "discovery.addons.mozilla.org",
  "input.mozilla.org",
  "install.mozilla.org",
  "oauth.accounts.firefox.com",
  "profile.accounts.firefox.com",
  "support.mozilla.org",
  "sync.services.mozilla.com",
  "testpilot.firefox.com",
  ];

  function isRestrictedURL(u) {
    try {
      if (typeof u === "string") u = new URL(u);
      return u.protocol === "https:" && domains.includes(tld.normalize(u.hostname || ""));
    } catch (e) {
      return false;
    }
  }
}