JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="frame" sandbox></iframe>

   <script type="text/javascript" src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
   <script type="text/javascript" src="https://rawgit.com/showdownjs/showdown/develop/dist/showdown.min.js"></script>

JavaScript

var md = '###Hello Word <script>alert("!")<\/script>';
       var match = md.match(/<script\b[^<]*(?:(?!<\/script>)<[^<]*)*<\/script>/gi);
       
       if(match && match.length) {
       	console.log('Aqui existe script, devemos emitir um erro para o cĂłdigo malicioso');
        return;
       }
       
       var converter = new showdown.Converter();
       var MDtoHTML = converter.makeHtml(md)
       var ifrm = $('#frame')
       ifrm.attr('srcdoc', MDtoHTML);