Source

File: wp-includes/update.php

function wp_get_update_data() {
	$counts = array(
		'plugins'      => 0,
		'themes'       => 0,
		'wordpress'    => 0,
		'translations' => 0,
	);

	$plugins = current_user_can( 'update_plugins' );

	if ( $plugins ) {
		$update_plugins = get_site_transient( 'update_plugins' );

		if ( ! empty( $update_plugins->response ) ) {
			$counts['plugins'] = count( $update_plugins->response );
		}
	}

	$themes = current_user_can( 'update_themes' );

	if ( $themes ) {
		$update_themes = get_site_transient( 'update_themes' );

		if ( ! empty( $update_themes->response ) ) {
			$counts['themes'] = count( $update_themes->response );
		}
	}

	$core = current_user_can( 'update_core' );

	if ( $core && function_exists( 'get_core_updates' ) ) {
		$update_wordpress = get_core_updates( array( 'dismissed' => false ) );

		if ( ! empty( $update_wordpress )
			&& ! in_array( $update_wordpress[0]->response, array( 'development', 'latest' ), true )
			&& current_user_can( 'update_core' )
		) {
			$counts['wordpress'] = 1;
		}
	}

	if ( ( $core || $plugins || $themes ) && wp_get_translation_updates() ) {
		$counts['translations'] = 1;
	}

	$counts['total'] = $counts['plugins'] + $counts['themes'] + $counts['wordpress'] + $counts['translations'];
	$titles          = array();

	if ( $counts['wordpress'] ) {
		/* translators: %d: Number of available WordPress updates. */
		$titles['wordpress'] = sprintf( __( '%d WordPress Update' ), $counts['wordpress'] );
	}

	if ( $counts['plugins'] ) {
		/* translators: %d: Number of available plugin updates. */
		$titles['plugins'] = sprintf( _n( '%d Plugin Update', '%d Plugin Updates', $counts['plugins'] ), $counts['plugins'] );
	}

	if ( $counts['themes'] ) {
		/* translators: %d: Number of available theme updates. */
		$titles['themes'] = sprintf( _n( '%d Theme Update', '%d Theme Updates', $counts['themes'] ), $counts['themes'] );
	}

	if ( $counts['translations'] ) {
		$titles['translations'] = __( 'Translation Updates' );
	}

	$update_title = $titles ? esc_attr( implode( ', ', $titles ) ) : '';

	$update_data = array(
		'counts' => $counts,
		'title'  => $update_title,
	);
	/**
	 * Filters the returned array of update data for plugins, themes, and WordPress core.
	 *
	 * @since 3.5.0
	 *
	 * @param array $update_data {
	 *     Fetched update data.
	 *
	 *     @type array   $counts       An array of counts for available plugin, theme, and WordPress updates.
	 *     @type string  $update_title Titles of available updates.
	 * }
	 * @param array $titles An array of update counts and UI strings for available updates.
	 */
	return apply_filters( 'wp_get_update_data', $update_data, $titles );
}