Slashdot Mirror
Microsoft Tries To Censor Bing Vulnerability
An anonymous reader writes "Microsoft's Bing search engine has a vulnerability with its cash-back promotion, which impacts both merchants and customers. In traditional Microsoft fashion, the company has responded to the author of the breaking Bing cash-back exploit with a cease & desist letter, rather than by fixing the underlying security problem. It is possible for a malicious user to create fake Bing cash-back requests, resulting in not only fake cash-back costs for the merchant, but also blocking legitimate customers from receiving their cash-back from Bing. The original post is currently available in Bing's cache, although perhaps not for long. But no worries, the author makes it clear that the exploit should be painfully obvious to anyone who reads the Bing cash-back SDK."
It seems like people have still not learned to never trust anything from the user. This reminds me of some trivially exploitable web merchants years ago. The would store the entire shopping basket, including prices, in the user's cookies. User simply modifies their cookies so that everything costs $1 or $0.01 and they could order a dozen cpus / t-shirts / whatever for a few bucks.
is the line from the letter
"cease and desist the posting in any location of the material and information contained in this post"
Seeing as it is their SDK that contains the details of this "feature", are they going to send themselves a C&D and then pull the SDK?
like this you mean?
Breaking Bing Cashback
Posted November 4th, 2009 by Samir
I've never bought anything using Bing Cashback, but the balance of my account is $2080.06. Apparently, I placed two $1 orders on January 24th of this year, and spent another $104,000 on October 24th. Let's see how these transactions might have "accidentally" got credited to my account.
First, we need to try to figure out how transactions get into Bing Cashback. Microsoft posted some documentation here. The explanation of how a merchant reports transactions to Bing starts on page 20. Merchants have a few options for reporting, but Bing suggests using a tracking pixel. Basically, the merchant adds a tracking pixel to their order confirmation page, which will report the the transaction details back to Bing. The request for the tracking pixel looks something like this:
https://ssl.search.live.com/cashback/pixel/index?
jftid=0&jfoid=&jfmid=
&m[0]=&p[0]=&q[0]=
This implementation, while easy for the merchant, has an obvious flaw. Anyone can simulate the tracking pixel requests, and post fake transactions to Bing. I'm not going to explain exactly how to generate the fake requests so that they actually post, but it's not complicated. Bing doesn't seem to be able to detect these fake transactions, at least not right away. The six cents I earned in January have "cleared," and I'm guessing the remaining $2080 will clear on schedule, unless there is some manual intervention.
Even if Bing detects these fake transactions at some point in the future, the current implementation might have another interesting side effect. I haven't done enough work to say it with confidence, but a malicious user might be able to block another user's legitimate purchases from being reported correctly by Bing (I only tried this once, but it seemed to work). Posting a transaction to Bing requires sending them an order ID in the request. Bing performs a reasonable sanity check on the order ID, and will not post a transaction that repeats a previously reported order ID. When a store uses predictable order ID's (e.g. sequential), a malicious user can "use up" all the future order ID's, and cause legitimate transactions to be ignored. Reporting would be effectively down for days, causing a customer service nightmare for both Bing and the merchant.
Based on what I've found, I wouldn't implement Bing Cashback if I were a merchant. And, as an end user and bargain hunter, it does not seem smart to rely on Bing Cashback for savings. In our next blog post, I'll demonstrate some other subtle but important reasons to avoid using Bing Cashback.
Security through obscurity is not about relying on secrecy of data, but about relying on secrecy of the algorithm or implementation. Those two things are different.
If you do not make the distinction between data/information secrecy and design/algorithm/protocol/implementation secrecy, then you do not understand what security is.