------------------------------------------------------------------------ Cross-Site Scripting vulnerability in Simple Membership WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ A Cross-Site Scripting vulnerability was found in the Simple Membership 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-20160712-0016 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Simple Membership [2] WordPress Plugin version 3.2.8. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ This issue is resolved in Simple Membership version 3.2.9 [3]. ------------------------------------------------------------------------ Introduction ------------------------------------------------------------------------ The Simple Membership [2] WordPress Plugin adds membership functionality to your site. Protect members only content using content protection easily. A Cross-Site Scripting vulnerability was found in the Simple Membership 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. ------------------------------------------------------------------------ Details ------------------------------------------------------------------------ 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. class.swpm-members.php: 'edit' => sprintf('Edit', $_REQUEST['page'], $item['member_id']), [...] onclick="return confirm(\'Are you sure you want to delete this entry?\')">Delete', $_REQUEST['page'], $item['member_id']), class.swpm-membership-levels.php: 'edit' => sprintf('Edit', $_REQUEST['page'], $item['id']), [...] onclick="return confirm(\'Are you sure you want to delete this entry?\')">Delete', $_REQUEST['page'], $item['id']), admin_members_list.php: admin_all_payment_transactions.php: 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 ------------------------------------------------------------------------
------------------------------------------------------------------------ References ------------------------------------------------------------------------ [1] https://sumofpwn.nl/advisory/2016/cross_site_scripting_vulnerability_in_simple_membership_wordpress_plugin.html [2] https://wordpress.org/plugins/simple-membership/ [3] https://downloads.wordpress.org/plugin/simple-membership.zip