Adgregate is a "TechCrunch 50" startup that recently signed a distribution deal with Google/DoubleClick . As a service, they offer a "viral widget" intended to be hosted on untrusted third-party sites through which consumers can enter their credit card information. According to their website, they offer over 1.2 million products through this service. More details can be found at .
Consumers are able to validate that their data entry is secure by clicking on a "validate this widget" button within the widget. However, the widget proves itself by simply POSTing an (apparently) fixed (per ShopAd id) string to a fixed URL, which is trivially vulnerable to replay attacks. For example, see the (clearly bogus) widget at . Of course, a more serious attacker would spend more time reproducing the look-and-feel of the adgregate widget.
Here's the relevant HTML that fakes the validation functionality:
<form method="POST" action="https://secure.adgregate.com/AuthenticWidget.aspx"> <input type="hidden" name="widgetvalid" value="1w23e4r5-ijhyffrd"> <input type="submit" value="Validate this ShopAd!"> </form>
(Bob Ippolito first alerted me to this service and provided the above HTML form snippet.)
 http://www.techcrunch.com/2009/04/06/adgregate-markets-scores-distribution-deal-with-googles-doubleclick/  http://adgregate.com/web/demo/  http://shinobi.dempsky.org/~matthew/adgregate.html