Dactyloidae/toolkit/components/passwordmgr/test/subtst_master_pass.html

<h2>MP subtest</h2>
This form triggers a MP and gets filled in.<br>
<form>
Username: <input type="text"     id="userfield" name="u"><br>
Password: <input type="password" id="passfield" name="p"><br>
<script>
    // Only notify when we fill in the password field.
    document.getElementById("passfield").addEventListener("input", function() {
        parent.postMessage("filled", "*");
    });
</script>
</form>