WordPress 4.9.4 Fixes Critical Auto Update Bug in 4.9.3
by Jeff Chandler, WordPress Tavern
February 7, 2018
Hours after WordPress 4.9.3 was released, the WordPress development team followed it up with 4.9.4 to fix a critical bug with the auto update process. The bug generates a fatal PHP error when WordPress attempts to update itself.
This error requires [some] WordPress site owners and administrators to manually update to WordPress 4.9.4 by visiting your Dashboard and clicking the Update Now button on the Updates page. Alternatively, you can update by uploading the files via SFTP or by using WP-CLI.
Dion Hulse, WordPress lead developer, says managed hosts that apply updates automatically for their customers will be able to update sites as they normally do. This may explain why some users have reported that sites running 4.9.3 have automatically updated to 4.9.4 without issue.