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JavaScript
HTML
CSS
Result
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
    "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
    <title>cdata</title>
    <script type="text/javascript">
    //<![CDATA[
        
        window.onload = function(){
            
            alert('dkjfkldjskljf' + '</script>');
            alert('dkjfkldjskljf' + '&lt;/script&gt;');
            var a = '<h1>11</h1>';
            
            alert('&lt;');
            
                
            document.body.innerHTML = a;
        }
        
    //]]>
    </script>
</head>
    
<body>


</body>
</html>