------------------------------------------------------------------------ Cross-Site Request Forgery in Global Content Blocks WordPress Plugin ------------------------------------------------------------------------ Yorick Koster, July 2016 ------------------------------------------------------------------------ Abstract ------------------------------------------------------------------------ It was discovered that the Global Content Blocks WordPress Plugin is vulnerable to Cross-Site Request Forgery. Amongst others, this issue can be used to update a content block to overwrite it with arbitrary PHP code. Visiting a page or blog post that uses this content block will cause the attacker's PHP code to be executed. ------------------------------------------------------------------------ OVE ID ------------------------------------------------------------------------ OVE-20160712-0031 ------------------------------------------------------------------------ Tested versions ------------------------------------------------------------------------ This issue was successfully tested on Global Content Blocks [2] WordPress Plugin version 2.1.5. ------------------------------------------------------------------------ Fix ------------------------------------------------------------------------ There is currently no fix available. ------------------------------------------------------------------------ Introduction ------------------------------------------------------------------------ The Global Content Blocks [2] WordPress Plugin lets users create their own shortcodes to insert reusable code snippets, PHP or HTML including forms, opt-in boxes, iframes, Adsense code, etc, into pages and posts as well as widgets and directly into php content. Global Content Blocks is affected by Cross-Site Request Forgery. Amongst others, this issue can be used to update a content block to overwrite it with arbitrary PHP code. Visiting a page or blog post that uses this content block will cause the attacker's PHP code to be executed. ------------------------------------------------------------------------ Details ------------------------------------------------------------------------ The issue exists due to the fact that Global Content Blocks does not use the Cross-Site Request Forgery protection provided by WordPress. Actions with Global Content Blocks have a predictable format, thus an attacker can forge a request that can be executed by a logged in Administrator. In order to exploit this issue, the attacker has to lure/force a logged on WordPress Administrator into opening a malicious website. ------------------------------------------------------------------------ Proof of concept ------------------------------------------------------------------------ The following proof of concept will update/overwrite the content block with id 1. In order to run the attacker's PHP code, a page/blog needs to be viewed that contains this content block (eg, [contentblock id=1]). ------------------------------------------------------------------------ References ------------------------------------------------------------------------ [1] https://sumofpwn.nl/advisory/2016/cross_site_request_forgery_in_global_content_blocks_wordpress_plugin.html [2] https://wordpress.org/plugins/global-content-blocks/