It was announced on wordpress.org on July 23 that version 4.2.3 of WordPress was released. Being a point release, in most instances this update will be automatically applied to your site. However, if you have automatic point release updates turned off, be sure to manually apply this update. The wordpress.org post provides instructions for the process.
It is a security release addressing problems in WordPress versions 4.2.2 and earlier where a cross-site scripting vulnerability was uncovered. This XSS vulnerability, could allow users with the Contributor or Author role to compromise a site.
WP Tavern, one of my favorite go-to sources for breaking news in the world of WordPress, offers another great perspective on this release by Sarah Gooding. Check out her post here.