FYI. WordPress released a security and maintenance release yesterday. It includes 10 fixes and enhancements including preparing users for the minimum PHP version which will be coming in WordPress 5.2. Starting with WordPress 5.2 you will need to have PHP 5.6 or later to be able to upgrade.
More information on this release is available at: https://wordpress.org/news/2019/03/wordpress-5-1-1-security-and-maintenance-release/
This security update should happen automatically if you have not turned off automatic updates. You can also update manually via Dashboard > Updates.