The getOrderByStatusUrlKey function in the Mage_Rss_Helper_Order class in app/code/core/Mage/Rss/Helper/Order.php in Magento Enterprise Edition before 1.14.2.3 and Magento Community Edition before 1.9.2.3 allows remote attackers to obtain sensitive order information via the order_id in a JSON object in the data parameter in an RSS feed request to index.php/rss/order/status.
https://magento.com/security/patches/supee-7405
http://www.securityfocus.com/archive/1/537601/100/0/threaded