<script>alert(1);</script>

dabblet.css

/**
 * <script>alert(1);</script>
 */

body {
	background-repeat: no-repeat;
	background-image: url(http://arnor.io/site_media/static/img/highlight.png);
	background-position: center top;
	background-color: #2a292a;
}

dabblet.html

<script type="text/javascript">alert(1);</script>

settings.json

{"view":"split-vertical","prefixfree":"1","page":"html"}

">

"><script type="text/javascript">alert(1);</script>