As you may know, WordPress has introduced automatic updates since version 3.7. But I have to admit that I’m a control freak, meaning – in this case – that I prefer manual updates, made on my own terms when I want. There are a couple of ways in which to disable automatic updates. I’ll list them below.
Disable WordPress automatic updates using wp-config.php
Add the following snippet in wp-config.php, just before the /* That's all, stop editing! Happy blogging. */ line.
define('AUTOMATIC_UPDATER_DISABLED', true);
Disable WordPress automatic updates using functions.php
Add the following snippet in functions.php file
add_filter('auto_upgrader_disabled', '__return_true');
If you are using a child theme, add the snippet in the child theme’s functions.php file
Personally, I recommend the first method because it’s not theme-dependent as the second one.