Its developers Automattic were released last night on new edition WordPress 4.9.5:
The updated CMS update (from the content management system) is a maintenance version and it comes to fix 28 errors 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 upgrade it would be good to get a full backup.