WordPress 4.3.1 is a security fix for some cross-site scripting vulnerabilities and a potential privilege issue.
Per WordPress.org:
WordPress versions 4.3 and earlier are vulnerable to a cross-site scripting vulnerability when processing shortcode tags (CVE-2015-5714). Reported by Shahar Tal and Netanel Rubin of Check Point. A separate cross-site scripting vulnerability was found in the user list table. Reported by Ben Bidner of the WordPress security team. Finally, in certain cases, users without proper permissions could publish private posts and make them sticky (CVE-2015-5715). Reported by Shahar Tal and Netanel Rubin of Check Point.
Update all your WordPress installations.