WordPress.org developers have just released the WordPress 4.9.2 update (Billy Tipton) to fix some security gaps.
The change log starts by stating that all older versions of WordPress are affected by a vulnerability XSS in the Flash fallback files of MediaElement 4.x, a library included in the WordPress 4.9.
In addition to the above security issue, the new WorPress 4.9.2 contains other 21 bug fixes that you can see in official announcement.
Of course as with any other update regardless of vendor, it is recommended to upgrade immediately. You can make a new one installation with the package, or upgrade automatically through the admin panel of the web application.
https://wordpress.org/download/
