One issue was discovered by researchers from Web security firm Sucuri and stems from improper validation of email addresses in the customer registration form.
The issue is rated as critical because the rogue code can hijack an administrator's authenticated session or can instruct his browser to perform a rogue action on the website, such as adding another administrator account with attacker-supplied credentials.
The vulnerability affects Magento Community Edition prior to version 126.96.36.199 and Magento Enterprise Edition prior to version 188.8.131.52. Magento also released a patch bundle last week called SUPEE-7405 that can be applied to older versions.
The bundle also includes fixes for 19 other flaws, including a similar stored XSS issue in the order comments form and one in the processing of the HTTP_X_FORWARDED_FOR header for the customer's IP address. Other issues fixed include information leaks, CAPTCHA bypasses, cross-site request forgery issues, malicious file uploads and denial-of-service against the newsletter function.
Some of these flaws also affect Magento 2.x CE and EE. Version 2.0.1 was released for both editions in order to address them, along with some critical stored XSS flaws that only exist in the 2.x versions.
"If you’re using a vulnerable version of Magento, update/patch as soon as possible," said Marc-Alexandre Montpas, the Sucuri researcher who found one of the stored XSS flaws, in a blog post Friday.
According to the company that develops the e-commerce platform, Magento is used by over 200,000 companies, including many popular brand owners. A 2015 survey of the top 1 million websites by traffic found that Magento is used by around 30 percent of their online shops, making it the most popular e-commerce platform.
Magento-based websites have been the target of large-scale attacks before, so they represent an attractive target for attackers. In October, thousands of online shops running the platform were infected with the Neutrino exploit kit.