Pierluigi Paganini January 26, 2016

A stored cross-site scripting vulnerability in Magento exposes millions of e-commerce websites at risk of takeover, update your platform as soon as possible

Once again a vulnerability in the popular Magento e-commerce platform opens at risk of hijacking attacks millions of online merchants. According to the experts at Sucuri, the Magento e-commerce platform was affected by a stored cross-site scripting (XSS) vulnerability. All the versions of Magento Community Edition and Enterprise Edition prior to 1.9.2.3 and 1.14.2.3 are affected by this vulnerability that could be easily exploited by a remote attacker.

“During our regular research audits for our Cloud-based WAF, we discovered a Stored XSS vulnerability affecting the Magento platform that can be easily exploited remotely. We notified the Magento team and worked with them to get it fixed.” states an advisory published by Sucuri.

The experts ethically reported the vulnerability to the Magento security team to give it the possibility to develop a fix.

Magento admitted the flaw and published an advisory.

“During customer registration on the storefront, a user can provide an email address that contains JavaScript code. Magento does not properly validate this email and executes it in Admin context when viewing the order in the backend. This JavaScript code can steal an administrator session or act on behalf of a store administrator.” states the advisory published by Magento.

The flaw could be exploited by attackers to embed malicious JavaScript code inside the customer registration forms, the platform executes the scripts in the context of the administrator account allowing the attacker to gain the control of the server hosting the e-commerce platform.

“The buggy snippet is located inside Magento core libraries, more specifically within the administrator’s backend,” continues the Sucuri advisory. “Unless you’re behind a WAF or you have a very heavily modified administration panel, you’re at risk. As this is a Stored XSS vulnerability, this issue could be used by attackers to take over your site, create new administrator accounts, steal client information, anything a legitimate administrator account is allowed to do.”

The issue affects the code present in the form app/design/adminhtml/default/default/template/sales/order/view/info.phtml, in particular the experts noticed the use of  the getCustomerEmail method’s that returns value to the administration panel.

This piece of code looked similar to the one Sucuri has found in the WordPress Jetpack plugin a couple months ago, the experts focused their analysis on the validation mechanism implemented by Magento.

The analysis of the code used to validate the input revealed that two different forms of emails were accepted:

• Regular ones, similar to what we had found in WordPress (no double quotes, no ‘<‘ sign, etc.)
• Quoted string format, which accepts pretty much any printable characters (except for space characters, where it only allows regular spaces to be used) as long as it’s surrounded by two double-quotes

Ops … this means that by using an email like “><script>alert(1);</script>”@sucuri.net as and submitting an order it was possible to trigger the XSS flaw within the Magento Core..

In this way the experts triggered an XSS in Magento Core.

There is no time to waste, Magento administrator should install the update as soon as possible.

Pierluigi Paganini

(Security Affairs – Magento, stored cross-site scripting (XSS))