[NEWS] Arbitrary Price Manipulation in CartMan Shopping Software

From: support@securiteam.com
Date: 12/20/02

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    Date: 20 Dec 2002 01:16:28 +0200
    
    

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      Arbitrary Price Manipulation in CartMan Shopping Software
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.cartman.nethut.no/> Per Magne Knutsen's CartMan is a
    PHP-based multilingual, standalone web-based shopping cart application. A
    vulnerability in the product allows remote attackers to manipulate the
    price of products being sold by the software.

    DETAILS

    Vulnerable systems:
     * CartMan version 1.04

    When adding items to the CartMan shopping cart, it uses a URL similar in
    structure to the following:

    cartman.php?action=add&id=1234&descr=My%20Product&price=250&quantity=1

    The problem is an attacker can generate such a request by hand and set the
    price parameter (price=250 in the above URL) to any price desired. The
    following rewritten URL will add the "My Product" item listed as $250 to
    the attackers shopping cart at a price of $1:

    cartman.php?action=a
    dd&id=1234&descr=My%20Product&price=1&quantity=1

    Analysis:
    In cases where software is made available for download immediately after
    automated credit card validation, remote attackers can purchase such
    software for any price desired.

    Vendor response:
    Knutsen said, "A temporary fix that conceals how CartMan actually works
    has been suggested to my customers. The "fix" is available in the
    documentation file of an up-coming update of CartMan. Please see
    <http://www.cartman.nethut.no/development/documentation.html>
    http://www.cartman.nethut.no/development/documentation.html . The relevant
    section is in the section Frequently Asked Questions, and reads like this:

    - --- extract start ---

    "How can I create a product-link to CartMan without the price and product
    ID showing in the browser's address field?"
    You can also pass information to CartMan via a FORM in your webpage, not
    just by links. Remember to include all the fields. An example, that also
    uses JavaScript is used in the index.html page that comes with this
    distribution. Click on the Dreamweaver link to see it in action. The link
    calls a JavaScript on the page, that in turn submits an invisible FORM on
    the same page.

    - --- extract end ---"

    Disclosure timeline:
    11/04/2002 Issue disclosed to iDEFENSE
    11/22/2002 Author notified, Per Magne Knutsen (pknutsen@nethut.no)
    11/23/2002 Response from Author
    11/25/2002 iDEFENSE clients notified
    12/16/2002 Coordinated Public Disclosure

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:listserv@idefense.com>
    iDEFENSE Labs, the vulnerability was discovered by
    <mailto:steven.dowd@dowd.co.uk> Steven Dowd.

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