WordPress 4.3.1 is now available. This is a security release for all previous versions and it is strongly suggested that you update your sites immediately.
4.3.1 addresses three critical issues: two cross-site scripting vulnerabilities and a potential privilege escalation issue.
WordPress versions 4.3 and earlier are currently vulnerable to a cross-site scripting vulnerability when processing shortcode tags. A separate cross-site scripting vulnerability was found in the user list table and in certain cases users without proper permissions could publish private posts and make them sticky.
Download WordPress 4.3.1 or venture over to Dashboard -> Updates and simply click “Update Now”.
Its a good practice to Backup your WordPress before you upgrade. That way if anything goes wrong, you can easily revert your site back. Here we have listed some backup plugins for you.