Modify WordPress attachment ajax query

wp-attachment-query-args-update.php

<?php
/**
 * Show last 5 attachments in media popup
 */

/**
 * Attachment query arguments
 * @param  array $args Query arguments
 * @return array       Update query argumnets
 */
function op_update_attachment_args( $args ) {
    $args['posts_per_page'] = 5;
    $args['order'] = 'ASC';
    return $args;
}
add_filter( 'ajax_query_attachments_args', 'op_update_attachment_args' );