import org.concordion.api.extension.ConcordionExtender
import org.concordion.api.extension.ConcordionExtension

class CustomExtension extends ConcordionExtension {

    @Override
    public void addTo(ConcordionExtender concordionExternder) {
        concordionExtender.withEmbeddedJavaScript("first < second && third");
        concordionExtender.withEmbeddedCSS("body > p");
    }

}

<script type="text/javascript">first &lt; second &amp;&amp; third</script>
<style>body &gt; p</style>