WordPress 4.0 was released on 4th September 2014.

Update to WordPress 4.0 using the same process as shown for WordPress 3.6

Update to WordPress 3.6

Remember

Before applying any update remember to take a backup and confirm that the backup file will unpack.

See also

• WordPress 4.0 “Benny”
• Perform backups
• You should also update the oik base plugin to version 2.2 or higher.
• While you’re at it update other oik plugins from WordPress.org