How to Prevent Data Leakage on Your Website

June 14th, 2021 | By Jscrambler | 4 min read

How to Prevent Data Leakage on Your Website? If you are familiar with the concept of data leakage, you are likely also familiar with its consequences. But what about the mechanics behind it?

These are the two questions we will explore in this blog post so that you can learn how to effectively prevent data leakage on your website.

Why do websites leak data?

We need to understand how the average modern website works.

If we look at the latest statistics, we see that around 70% of all the scripts running on the average website come from third parties. Thus, companies only have 30% of the website’s code written and maintained internally.

If we zoom into this first-party code, we will find that it’s often composed of JavaScript frameworks and libraries like React and Angular.

These hundreds of pieces of third-party code lead to a complex supply chain. Therefore, they created a security blindspot for companies. Consequently, attackers could leverage this vulnerability to leak data.

But how exactly can attackers achieve this?

One key thing about third-party scripts is that they have the same power as all your first-party code.

They can access any type of data, tamper with your existing code, and even tamper with how your users interact with your website. Hence the problem of the web supply chain.

The web supply chain and data leakage

From code libraries to third-party services like chatbots and more, when you add up all these pieces of external code, you quickly get to the point where you have little to no visibility over what code you’re running on your website.

The issue comes because websites deal with sensitive information like credit card details, social security numbers, and private health information. So, when a user inputs and submits that data on any given website, it will invariably pass through the chaotic client side. And if companies don’t have visibility over the code they are running, they can’t be sure if any of the third-party scripts ever try to intercept and leak that sensitive data.

Attackers are using this security blindspot to launch web supply chain attacks. These attacks are increasingly popular because if an attacker manages to change a third-party script, they can inject arbitrary code into a website and do whatever they want. Plus, that code will affect all the users on that website and all the other websites that use that script.

Web supply chain attacks are also popular because attackers don't have to directly target the main website. They can go after its weakest link—the third-party vendor that is being used on the page—and leverage the fact that they might have fewer resources dedicated to security.


How to protect the web supply chain and prevent data leakage

The first step to preventing data leakage is gaining visibility into what’s happening on the client side. This means you monitor each script in real-time and know its specific behaviors.

An essential aspect here is knowing if and when a script is sending data out, what specific types of data are being sent out, and where the data is being sent out. Without this information, you can’t know whether a network connection is legitimate or an attempt to leak your users’ data.

But visibility is only part of the solution. A preventive approach to data leakage requires having control over all the different behaviors of your website scripts and being able to restrict them by default.

While approaches like Content Security Policy might seem to solve this problem, they are insufficient to tackle data leakage. Other strategies, like Web Application Firewalls or browser defenses, also fall short.

Finding the right solution for this problem requires an in-depth security approach that provides visibility and control.

To gain visibility, a good first step is to do an inventory of all the scripts that are running on your website as well as all the network connections that they are making. This allows you to get a clear picture of how your client-side is built, what your exposure to web supply chain risk is, and how your users' data is flowing through your client-side.

To gain control, you need an approach that allows you to restrict every possible behavior of your third-party scripts. Jscrambler Webpage Integrity provides a granular rules engine that gives you this level of control while not interfering with the experience of your end-users.

You can also protect your source code against data leakage attacks by using Jscrambler's Data Exfiltration Prevention countermeasure so that if someone tries to debug or tamper with your source code, all network connections are immediately blocked to protect your users' data.


The leader in client-side Web security. With Jscrambler, JavaScript applications become self-defensive and capable of detecting and blocking client-side attacks like Magecart.

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