Description
WordPress is prone to a cross-site scripting vulnerability because it fails to properly sanitize user-supplied input. An attacker may leverage this issue to execute arbitrary script code in the browser of an unsuspecting user in the context of the affected site. This can allow the attacker to steal cookie-based authentication credentials and launch other attacks. WordPress versions 3.9.x ranging from 3.9 and up to (and including) 3.9.9 are vulnerable.
Remediation
Update to WordPress version 3.9.10 or latest
References
https://www.incapsula.com/blog/incapsula-blocks-xss-vulnerability-wordpress-4-4-1.html
https://twitter.com/brutelogic/status/685105483397619713
Related Vulnerabilities
WordPress Plugin WP Safe Search 'v1' Parameter Cross-Site Scripting (0.7)
MediaWiki Other Vulnerability (CVE-2005-2215)
Vanilla Forums Cross-Site Request Forgery (CSRF) Vulnerability (CVE-2017-1000432)
OpenSSL 7PK - Security Features Vulnerability (CVE-2015-1793)
WordPress Plugin OAuth Single Sign On-SSO (OAuth Client) Cross-Site Scripting (6.20.2)