A security hole in some web-based shopping cart systems allows shoppers to edit the data and buy items at reduced prices, according to an ISS (Internet Security Systems) X-Force security alert issued this week. According to X-Force, 11 shopping cart applications used by e-commerce sites are vulnerable to this kind of malicious tampering. Some shopping cart applications use hidden fields in HTML forms to hold parameters for goods in an online store, and this is one potential security hole. If the attacker changes the price in the form on a local machine then loads the page into the browser, the item can be added to the cart at the modified price. If hidden discount fields are used it's also possible to modify these and get discounts on items without modifying the price in the form. From the vendors point of view this gets really nasty if credit card orders are processed in real time, and it's difficult to verify that the correct price is being used before the credit card is charged. X-Force also says that price changing is possible where an item's price is listed in a URL. "When clicking a link, the CGI program will add the item to the shopping cart with the price set in the URL. Simply changing the price in the URL will add the item to the shopping cart at the modified price. Shopping cart software should not rely on the web browser to set the price of an item." Most of the sites affected have begun modifying their software to plug the holes, says X-Force. ® Further Information: xforce.iss.net