<!DOCTYPE html>
<html>
<head><title>Page with access to document.cookie</title>
</head>
<body>
    <div>Cookie Read: <span id="readCookie"></span></div>
    <script type="text/javascript">
        cookie = document.cookie;
        document.cookie = "name=browser";
        parent.window.postMessage("cookies are R/W", "*");
    </script>
</body>
</html>