Source

File: wp-admin/includes/update.php

function find_core_auto_update() {
	$updates = get_site_transient( 'update_core' );
	if ( ! $updates || empty( $updates->updates ) ) {
		return false;
	}

	require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';

	$auto_update = false;
	$upgrader    = new WP_Automatic_Updater;
	foreach ( $updates->updates as $update ) {
		if ( 'autoupdate' !== $update->response ) {
			continue;
		}

		if ( ! $upgrader->should_update( 'core', $update, ABSPATH ) ) {
			continue;
		}

		if ( ! $auto_update || version_compare( $update->current, $auto_update->current, '>' ) ) {
			$auto_update = $update;
		}
	}
	return $auto_update;
}