uploader.php

См. документацию.

<?php

class CFileUploader extends \Bitrix\Main\UI\Uploader\Uploader
{
    public function __construct($params, $doCheckPost = true)
    {
        parent::__construct($params);
        if ($doCheckPost !== false)
        {
            $this->checkPost(($doCheckPost === true || $doCheckPost == "post"));
        }
    }
}