All users running WordPress are required to upgrade to patch a security hole.
From https://wordpress.org/news/2015/09/wordpress-4-3-1/
WordPress 4.3.1 is now available. This is a security release for all previous versions and we strongly encourage you to update your sites immediately.
This release addresses three issues, including two cross-site scripting vulnerabilities and a potential privilege escalation.
- 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.
Our thanks to those who have practiced responsible disclosure of security issues.
WordPress 4.3.1 also fixes twenty-six bugs. For more information, see the release notes or consult the list of changes.
Download WordPress 4.3.1 or venture over to Dashboard → Updates and simply click “Update Now.” Sites that support automatic background updates are already beginning to update to WordPress 4.3.1.