navigation-api/navigation-methods/sandboxing-navigate-sibling.html

<!doctype html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<iframe id="i" src="/common/blank.html" sandbox="allow-same-origin"></iframe>
<iframe id="i2" src="resources/navigate-sibling.html" sandbox="allow-scripts allow-same-origin"></iframe>

<script>
async_test(t => {
  window.onload = t.step_func(() => {
    i2.contentWindow.navigateSibling();

    i.onload = t.step_func_done(() => {
      const destinationURL = (new URL("/common/blank.html?2", location.href)).href;
      assert_equals(i.contentWindow.location.href, destinationURL);
      assert_equals(i.contentWindow.navigation.currentEntry.url, destinationURL);
    });
  });
}, "A sandboxed iframe can use its parent's navigation object to call navigate(), as long as allow-same-origin is present");
</script>