Description
WordPress is prone to a cross-domain Flash injection vulnerability. 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, allowing the attacker to steal cookie-based authentication credentials, or to fool a user into inserting credentials on a fake Flash form. WordPress versions 4.0.x ranging from 4.0 and up to (and including) 4.0.21 are vulnerable.
Remediation
Update to WordPress version 4.0.22 or latest
References
https://opnsec.com/2017/10/cve-2016-9263-unpatched-xsf-vulnerability-in-wordpress/
https://opnsec.com/2017/10/flashme-wordpress-vulnerability-disclosure-cve-2016-9263/
Related Vulnerabilities
WordPress Plugin Arlo training and event management system Cross-Site Scripting (2.1.7.1)
WordPress Plugin Timetable and Event Schedule by MotoPress Information Disclosure (2.3.19)
WordPress Plugin One User Avatar-User Profile Picture Unspecified Vulnerability (2.3.8)
WordPress Plugin Popup Anything-A Marketing Popup Cross-Site Scripting (2.0.3)