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 3.8.x ranging from 3.8 and up to (and including) 3.8.24 are vulnerable.
Remediation
Update to WordPress version 3.8.25 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
TYPO3 Unrestricted Upload of File with Dangerous Type Vulnerability (CVE-2017-14251)
WordPress Plugin MW WP Form Arbitrary File Upload (5.0.1)
Apache HTTP Server Other Vulnerability (CVE-2001-0731)
WordPress Plugin Citizen Space Cross-Site Scripting (1.0)
WordPress Plugin iThemes Security (formerly Better WP Security) Cross-Site Scripting (3.2.4)