osCommerce 2.3.4.1 has an incomplete '.htaccess' for blacklist filtering in the "product" page. Because of this filter, script files with certain PHP-related extensions (such as .phtml and .php5) didn't execute in the application. But this filter didn't prevent the '.pht' extension. Thus, remote authenticated administrators can upload '.pht' files for arbitrary PHP code execution via a /catalog/admin/categories.php?cPath=&action=new_product URI.