------------------------------------------------------------------------ Cross-Site Scripting vulnerability in Master Slider WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ A Cross-Site Scripting vulnerability was found in the Master Slider 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-20160712-0013 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Master Slider - Responsive Touch Slider [2] WordPress Plugin version 2.7.1. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ This issue is resolved in Master Slider version 2.8.0 [3]. ------------------------------------------------------------------------ Introduction ------------------------------------------------------------------------ The Master Slider [2] WordPress Plugin is a free responsive image and content slider with super smooth hardware accelerated transitions. It supports touch navigation with pure swipe gesture that you have never experienced before. It's a truly responsive and device friendly slider which works perfectly in all major devices. A Cross-Site Scripting vulnerability was found in the Master Slider 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 the file class-msp-list-table.php and is caused by the lack of output encoding on the page request parameter. The vulnerable code is listed below. return sprintf('%s',$_REQUEST['page'],'edit', $item['ID'], $item['title'] ); [...] $buttons .= sprintf( '%s',$_REQUEST['page'],'duplicate' ,$item['ID'], $paged_arg, __('duplicate') ); [...] $buttons .= sprintf( '%s', $_REQUEST['page'],'delete' ,$item['ID'], [...] $buttons .= sprintf( '%s',$_REQUEST['page'],'preview' ,$item['ID'], $item['ID'], __('preview') ); 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_master_slider_wordpress_plugin.html [2] https://wordpress.org/plugins/master-slider/ [3] https://downloads.wordpress.org/plugin/master-slider.2.8.0.zip