This is a security release for all previous versions and WordPress strongly encourage you to update your sites immediately.
The latest release of WordPress (Version 4.2.4 – released 4th August 2015) addresses a number of important issues, including three cross-site scripting vulnerabilities and a potential SQL injection that could be used to compromise your website.
It is important that you update your site as soon as possible in order to minimise risk of your site being hacked.
If you already had the previous version of WordPress installed, this new update should install automatically and your site administrator should have received an email informing of this.
If you haven’t updated for a while and are running an older version of WordPress, you will need to manually update it.