
<?php
#####################################################################################################################
#                                                                                                                   #
#                                                   ( About )                                                       #
#                                                                                                                   #
#       This is a real-life XSS that was found during bug hunting.                                                  #
#       The bounty amount was not big but the technical challenge was interesting enough to get me intrigued        #
#       I eventually managed to solve it and learnt more about how JavaScript works.                                #
#       I tought it would be interesting to share it.                                                               #
#       If you managed to solve it. DM me <a href="https://twitter.com/AboodNour">@aboodnour</a>                    #
#                                                                                                                   #
#####################################################################################################################

if(empty($_GET['payload'])){ highlight_file(__FILE__); exit;}


function clean_var($var){
    $var = preg_replace('#[^a-zA-Z0-9=\'\\\\/,.=\-&@_]#','',$var);
    return str_replace("'","\\'",$var);
}
?>

<html>
    <head>
        <title>XSS Challenge</title>
        <script>
            function Redirect(URL)
            {
                if (this.GoToPage)
                    this.GoToPage(URL);
                else
                    document.location.href = URL;
            }

            function Trigger()
            {
                var RedirectURL = '/?user_param=<?=clean_var($_GET['payload']);?>&';
                Redirect(RedirectURL);
            }
            //Trigger();
        </script>
    </head>

    <body>
        <h1>XSS Challenge</h1>
        <button onclick="Trigger();">Trigger XSS</button>
    </body>
</html>