Disabling update/download of new versions of default themes and plugins

WordPress comes with built-in themes and plugins. During each update check, the existence of new versions of these themes and plugins is also verified, and new themes that are part of the default WordPress configuration (a new theme every year) are downloaded.

WordPress has a setting that allows you to disable the update check and download of new bundled packages.

The list of packages included in the default bundle can be viewed in the global constant:

/**
 * Stores new files in wp-content to copy
 *
 * The contents of this array indicate any new bundled plugins/themes which
 * should be installed with the WordPress Upgrade. These items will not be
 * re-installed in future upgrades, this behaviour is controlled by the
 * introduced version present here being older than the current installed version.
 *
 * The content of this array should follow the following format:
 * Filename (relative to wp-content) => Introduced version
 * Directories should be noted by suffixing it with a trailing slash (/)
 *
 * @since 3.2.0
 * @since 4.7.0 New themes were not automatically installed for 4.4-4.6 on
 *              upgrade. New themes are now installed again. To disable new
 *              themes from being installed on upgrade, explicitly define
 *              CORE_UPGRADE_SKIP_NEW_BUNDLED as true.
 * @global array $_new_bundled_files
 * @var array
 * @name $_new_bundled_files
 */
global $_new_bundled_files;

$_new_bundled_files = array(
	'plugins/akismet/'          => '2.0',
	'themes/twentyten/'         => '3.0',
	'themes/twentyeleven/'      => '3.2',
	'themes/twentytwelve/'      => '3.5',
	'themes/twentythirteen/'    => '3.6',
	'themes/twentyfourteen/'    => '3.8',
	'themes/twentyfifteen/'     => '4.1',
	'themes/twentysixteen/'     => '4.4',
	'themes/twentyseventeen/'   => '4.7',
	'themes/twentynineteen/'    => '5.0',
	'themes/twentytwenty/'      => '5.3',
	'themes/twentytwentyone/'   => '5.6',
	'themes/twentytwentytwo/'   => '5.9',
	'themes/twentytwentythree/' => '6.1',
);

This constant is defined in the file wp-admin/includes/update-core.php.

The purpose of this constant is described in the comment below, translated as follows:

Disabling the download of new twenty* default themes

To disable the download of new default themes for new versions of WordPress (when WordPress is updated again), you need to define a constant in the wp-config.php file or in a mu plugin:

const CORE_UPGRADE_SKIP_NEW_BUNDLED = true;

Or like this:

define( 'CORE_UPGRADE_SKIP_NEW_BUNDLED', true );