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The ever-present threat of Magecart attacks

Do you know what “skimming” is? It’s a method that hackers use to gather sensitive information in online payment forums. Credit card numbers, email addresses, and user passwords are stolen. Magecart is a form of data skimming. The targets of these attacks are online shopping cart systems, the most common one being Magento. Attackers get a hold of the customers’ payment card information and abuse it for their own gains. The main way of doing this is compromising a third-party piece of software, usually from a VAR. Magecart hackers implant their malicious code into a website. Then they steal credit card information when a user enters their credentials during the checkout phase of shopping.

But why are shopping carts such an alluring target for these hackers? Because shopping carts collect your payment information. Hackers can do a lot of harm if they manage to tap into this data stream. The problem lies with the eCommerce sites. Why? They don’t check open-source (third-party) code for vulnerabilities when they build their eCommerce site. This is a recipe for disaster as sometimes this code comes with vulnerabilities that can easily be exploited. Are these Magecart attacks dangerous just for individual users? Not exactly. Even gigantic businesses like Ticketmaster’s United Kingdom Website, Puma’s Australian website, and even British Airways got attacked as reported by CNCB. As you can see, Magecart attacks are a huge threat for anyone, be it a small business or a large enterprise.

How do Magecart attacks work


For a Magecart attack to succeed, it needs to perform three actions:

  1. Access the website

    To inject the skimming code a hacker first needs to gain access to the targeted website. One way is to breach the defenses of the infrastructure or the server and then inject the skimmer. Another way includes targeting your third-party vendors. A third-party tag can be infected to run a malicious script on a site when it’s called in your browser. A hacker that achieves this then can then start skimming the data.

  2. Skimming sensitive information

    Many ways of capturing data exist. However, code that’s used for skimming is a piece of JavaScript code that finds personal information and collects it. An example of this is when a JavaScript intercepts the input of specific areas of a web form (credit card/CVV field). Magecart attacks even evolved over time. Hackers now conceal their malicious code inside a harmless code to avoid detection.

  3. Sending acquired information back to the hacker’s server

    Once a hacker gets to this part, the damage is already done. When they access the website and collect the data they need, you’ve lost. Hackers can now send this information to any place on the internet.

As you can see, Magecart hackers are dangerous. They can easily alter the Magento source or redirect the entire shopping cart to a malicious website by using injections. Is it easy to detect these attacks? It is if you’re ready to compare your entire eCommerce code stack one line at a time to see if anything was altered. A particularly nasty way Magecart attacks have been done includes uploading the malicious code to any unused GitHub project. Hackers that manage to take ownership of this project can then publish a new version of the code. One which contains malware. This propels the malware across a countless number of websites, spreading the infection further. Some security tools won’t even scan GitHub code. This way hackers and their malicious websites remain unnoticed, hiding in plain sight. 

Which vulnerabilities get targeted by Magecart attacks

This is the age of open-source development. Source code is publicly available and anyone can study it, change it, and improve it. A lot of websites today are built based on many open-source components (third-party code). You have 20 companies that make and operate the code you’re using for your website. The problem lies within the privileges granted to the 3rd party code. Third-party code usually has the same level of privilege as your own code. Why is this a problem? Because this third-party code is able to exfiltrate sensitive data that is entered by users. It can even redirect the user to another website. Customers aren’t aware of these technical issues. They don’t know what it means for a website that’s built with code that’s hosted by 50 different development groups/organizations. Any vulnerability that comes from an open-source component leaves your website vulnerable as well.

Some Magecart groups are evolving their techniques. An attack on the Shopper Approved website proved that these attacks are a serious threat. This particular attack abused the vendor’s customer scoring plug-in. The plug-in got used to rate all kinds of websites that displayed badges of honor. Shopper Approved quickly removed the malware once it was identified. But the malware managed to spread across many eCommerce sites nonetheless.

Others stick to attacking shopping carts. However, they use a new method to infect advertising banners. These hackers utilize ad servers. By doing this the ad server places the Magecart code into a specific webserver. Any user that views this ad in their browser gets infected. A code gets downloaded to their computer.

Lastly, you have hackers that plan extremely targeted and complex attacks. Instead of the quantity, they focus on quality. These hackers spend a lot of time studying the code and the infrastructure of one target. British Airways happened to be a victim of this particular attack. Hackers exploited the logic flow of internal applications. The infected script targeted their baggage claim information page. Magecart then stole all the data that wasn’t stored on any of the servers that were owned by British Airways. This is how an XSS attack compromised British Airways’ servers. Testing your applications and WebSockets for XSS vulnerabilities is a much easier task when you use solutions like NexDAST. You can read more about this specific type of attack on one of our blogs.

How to protect yourself and your business

Now we know how Magecart attacks work and what their primary targets are. How does one protect themselves and their business against them? Protecting against attacks like this can be difficult. Just auditing a website every now and then won’t help. Why? The problem comes from third-party tags which are not detected by auditing. An effective prevention technique is a zero-trust approach with JavaScript on a website. A policy that will block access to any sensitive information entered in both stored cookies and web forums by default is a good start. Then only a selected set of vetted script should be allowed to access sensitive data. This approach makes it so skimming code can’t get access to any sensitive information when it gets on a website.

Web browsers don’t offer this option in most cases. Yet, users can make sure they’re not a victim of Magecart attacks in a couple of ways:

  • Avoid smaller websites that may not have a high level of security as bigger, more known websites
  • Check your credit cards for charges (Hackers make small test charges to make sure the targeted credit card is still active)
  • Use secure payment systems like Apple Pay (They generate unique numbers for each transaction so that attackers can’t re-use an obtained number)

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