The automatic upgrade function of WordPress is usefull for most bloggers, as they always are reminded to keep WordPress and its extensions up to date. Anyhow, it can be very annoying for developers when customers and end-user make updates by their own, usually destroying something.

It is often recomendable to disable this notifications: Sometimes a Plugin or Theme must be extended or changed by the developer - automatic upgrades would destroy these changes. Some Plugins like Mailpress do not disable the automatic upgrade, though automatic upgrading usually leeds to huge data losses  🙁 Recently I had to learn this the hard way, but this is no excuse for incomplete backups, of course.

However the following functions can help:

1. Disable Plugin upgrades

You can disable special Plugins by pasting the following code into the Plugin itself:

add_filter('site_transient_update_plugins', 'cis_remove_plugin_update');
 
function cis_remove_plugin_update($value) {
	unset($value-\>response[ plugin_basename(__FILE__) ]);
	return $value;
}

You can alternativley paste some code into your functions.php-file of your Theme:

add_filter('site_transient_update_plugins', 'cis_remove_plugin_update');
 
function cis_remove_plugin_update($value) {
	$plugin_relative_path = "plugin_relative_path"; // this could be "akismet/akismet.php" for example
	unset($value->response[ $plugin_relative_path]);
	return $value;
}

You also can disable all Plugin upgrades, for example if you want to prevent customers from doing that:

remove_action ('load-update-core.php', 'wp_update_plugins');
add_filter ('pre_site_transient_update_plugins',create_function ('$a', "return null;"));

2. Disabling Theme Upgrades

Disable all Theme updgrades:

remove_action ('load-update-core.php', 'wp_update_themes');
add_filter ('pre_site_transient_update_themes',create_function ('$a', "return null;"));

3. Disable Core Updgrade

Note: You never should disable the Core-Upgrade of WordPress, as important security upgrades will be missed. However, if you need to do it for some reason:

add_filter ('pre_site_transient_update_core',create_function ('$a', "return null;"));