Coupons.com Shares Users' User IDs with Third Parties
A Closer Look at Coupons.com - Ben Edelman
This page shows how Coupons.com shares users' user IDs with third parties. Further discussion.
Coupons.com Prints Users' ID Numbers On Coupons
Every coupon printed from Coupons.com bears a series of small numbers around its four edges. These numbers include the user ID of the user who printed the coupon. The example coupon below was printed on my computer. Notice the repeated "35415364" -- my user ID. Further discussion.
Coupons.com Allows Third-party Web Sites to Retrieve User ID Numbers
Any web page can invoke the "GetDeviceID" method of Coupons.com's coupon-printing software. The web page then receives the user ID associated with the user's installation of Coupons.com software. The screenshot below shows confirmation via a demonstration page I wrote. Notice that the demonstration page -- part of my site, benedelman.org -- is able to retrieve my user ID. Notice also that this user ID matches the number shown on the face of each printed coupon (e.g. in the example above). Further discussion.
Coupons.com's Veri-fi site lets any third party check whether a given user has printed a given coupon
If the specified user has printed the specified coupon (i.e. the coupon is "valid"), Coupons.com shows a message to that effect.
If the specified user has never printed the specified coupon, Coupons.com calls the coupon "invalid."