WordPress has released a new maintenance/security update today to WordPress core: version 4.9.5. Version 4.9.5 comes with minor security and maintenance fixes which the WordPress core team deemed impactful enough to warrant a release.
For details on this release you may reference the official blog post on WordPress.org: https://wordpress.org/news/2018/04/wordpress-4-9-5-security-and-maintenance-release/
As with all maintenance/security related updates, WordPress has released patches for older functional versions as well. As a WP Engine customer, no action is required. Our team is already working to push out automatic updates to your site(s) to ensure they are in the next version. You will receive an email notification when the update has been completed. Our team is always attentive to our promise to provide a secure WordPress experience for all WP Engine customers.