Its developers Automattic were released last night on new edition WordPress 4.9.5:
The updated version of the popular CMS (from content management system) is a maintenance release and comes to fix 28 bugs of 4.9.4.
That's it change log says:
From the WordPress 4.9.5 release post: This maintenance release fixes 28 bugs in 4.9, including fixes for Customizer, media library, error notices, and some security fixes. Twenty Seventeen bundled theme and Hello Dolly bundled Plugin have also been updated.
Of course, as with any updates, you'll need to upgrade immediately, either by downloading it application from the official website, or from your admin panel in automatic mode.
Before proceeding with the upgrade, it would be a good idea to get a full backup.