------------------------------------------------------------------------ Cross-Site Scripting in Contact Bank WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ A Cross-Site Scripting vulnerability was found in the Contact Bank 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-20160724-0023 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Contact Bank - Contact Forms Builder [2] WordPress Plugin version 2.1.21. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ This issue is resolved in Contact Bank version 2.1.23 [3]. ------------------------------------------------------------------------ Introduction ------------------------------------------------------------------------ The Contact Bank [2] WordPress Plugin is a form builder plugin that lets you create contact forms in seconds with ease. A Cross-Site Scripting vulnerability was found in the Contact Bank 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 views/header.php and is caused by the lack of output encoding on the page request parameter. The vulnerable code is listed below. 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_in_contact_bank_wordpress_plugin.html [2] https://wordpress.org/plugins/contact-bank/ [3] https://downloads.wordpress.org/plugin/contact-bank.zip