Cybercriminals have devised a new method to hide credit card data siphoned from compromised online stores, experts from Sucuri observed Magecart hackers hiding data in JPG files to avoid detection and storing them on the infected site.
The new exfiltration technique was uncovered while investigating a Magecart attack against an e-store running the e-commerce CMS Magento 2.
“A recent investigation for a compromised Magento 2 website revealed a malicious injection that was capturing POST request data from site visitors. Located on the checkout page, it was found to encode captured data before saving it to a .JPG file.” reads the post published by Sucuri.
The researchers discovered a PHP code that was found injected to the file ./vendor/magento/module-customer/Model/Session.php. The attackers use the getAuthenticates function to load the rest of the malicious code onto the compromised environment.
The code stored the siphoned data in the image file “pub/media/tmp/design/file/default_luma_logo.jpg,” in this way it is easy to hide, access, and download the stolen information without rising suspicious.
The PHP code injected into the site leverages the Magento function getPostValue to capture the POST data within the checkout page, then the captured POST data is encoded with base64 before the PHP operator ^ is used to XOR the stolen data.
“To successfully capture the POST data, the PHP code needs to use the Magento code framework. It relies on the Magento function getPostValue to capture the checkout page data within the Customer_ POST parameter.” continues the post.
“Using the Magento function isLoggedIn, the PHP code also checks whether the victim that sent the POST request data is logged in as a user. If they do happen to be logged in, it captures the user’s email address.”
Customer_ parameter contains almost all of the information submitted by the victim on the checkout page, including full names and addresses, payment card details, telephone numbers, and user agent details.
Sucuri experts pointed out that captured data could be used for credit card fraud, spam campaigns, or spear-phishing attacks.
“Bad actors are always actively searching for new methods to prevent any detection of their malicious behavior on compromised websites.” concludes the post. “The creative use of the fake .JPG allows an attacker to conceal and store harvested credit card details for future use without gaining too much attention from the website owner.”
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(SecurityAffairs – hacking, Magecart)