Problematic JavaScript Vulnerabilities And Their Fixes Every Developer Should Know

A web developer’s ultimate goal is to not only develop a website or an app that is aesthetically and functionally stunning but highly secure as well. Cybersecurity is inevitable and no end-user would want to have an app that could breach or compromise their data security and integrity (no matter how useful the app is). With hackers and middlemen working on creative ways to explore vulnerabilities, it is on developers like us to take charge and be a step ahead of them. 

That’s why we should be aware of the vulnerabilities and security concerns during the coding stages. When we are familiar with the fundamental flaws associated with our code and programming languages, it would be simply easy for us to come up with workarounds, patches and even fixes. In today’s post, we are going to explore the vulnerabilities of JavaScript and see how we could overcome them. 

Let’s get started. 

Are JavaScript Vulnerabilities For Real?

No programming language is perfect and JavaScript is no exception. As far as JavaScript web development is concerned, there are tons of security aspects that can be exploited by hackers. The surprising part is this compromise can happen both on the server-side and client-side. When a JavaScript vulnerability is exploited, hackers can easily manipulate and steal data, redirect user sessions, modify data and do more. 

What Are The Types Of JavaScript Vulnerabilities?

Types of JavaScript Vulnerabilities


1. Cross-site Scripting Attacks

This is the most common vulnerability, where hackers manipulate HTML and JavaScript scripts and launch malicious payloads with the help of a user’s browser. Because the script sits in the browser, it gets embedded into web pages as well. Whenever the user visits the page and performs an action, the script is triggered. From identity theft to a data breach, this attack can cause companies, enterprises and individuals serious losses. 

2. Cross-site Request Forgery

In this, malicious commands that often get rejected by websites trick them into believing that the user accessing the website is genuine and authorized. This forged authorization will offer hackers the chance to access modules and aspects that remain denied to them otherwise. This causes consequences such as impersonation, identity theft, triggering of targeted attacks, modification of data through a victim’s credentials, exploitation of DSL routers and more.


JavaScript Vulnerabilities Every Developer Should Know 

Problematic JavaScript Vulnerabilities Every Developer Should Know

1) Source Code Security

This vulnerability can be exploited in tandem with other vulnerabilities. Since JavaScript is an interpreted language, there is no way you can seal your source code from being visible to the public. However, with obfuscation, you can slow down the time hackers would require to reverse engineer their attempts. 

The presence of libraries and packages is indeed a strength to javascript developers. However, it is also a major shortcoming because of the number of unknown vulnerabilities it brings to your ecosystem. If you are someone who prefers packages to accomplish even a small task, you are only increasing the web security risks.

One of the ideal ways to overcome concerns with source code is deploying airtight auditing tools. 

2) Unintentional Script Execution

A major chunk of unintentional script execution attacks features Cross-site Scripting. JavaScript’s Document Object Model allows scripts to be embedded in web pages and launched on the client-side. This even makes untrusted and unauthorized scripts get triggered for launch. If you’ve visited forums online and been able to read other people’s messages, understand that it was a security concern falling under the topic of unintentional script execution. 

3) Filtering Out Input

In several cases, you can filter out dangerous characters from users’ input to protect them from data manipulation. While this solution is good, it is not advisable to rely on this technique alone to prevent data manipulation as hackers can easily evade such input filters. 

4) Wrong Input Validation

Input or data that users provide on websites should be properly validated. For instance, phone number boxes should accept only numbers with exceptions to a few special characters like + and -. Email addresses should mandatorily have the symbol @ and end with .com. Such validation techniques could patch certain vulnerabilities to significant extents. 

5) Encoding User Input

Cross-site scripting attacks depend on supplying data that feature certain special characters for execution. These characters are used in underlying JavaScript, CSS or HTML pages. Because of this, browsers that are supposed to display the values or characters misinterpret them to be part of the code or programming. This is what empowers hackers to breakout of text fields and provide additional browser-side codes for triggering. 

This can be easily prevented by using escape codes for the special characters whenever browser-supplied data is returned as part of a response. 

6) Depend On Client-side Validation Only

The techniques we discussed so far ideally work on the client-side on browsers and web pages. However, hackers can often get creative and transmit data directly to servers, bypassing any and every client-side validation. This results in the uploading of malicious code or data onto the server. With no server-side validation protocol in place, the data that is stored could easily be corrupted, modified or completely replaced. 

The most practical fix to this is to implement client and server-side validations. 

7) Hacking Of Session Data

Malicious browser-side scripts are powerful and they can access all sorts of content returned to the browser by web applications. Cookies are part of such content that can be gained access to. Like you know, cookies contain some of our most confidential and private data and access to cookies means hackers can hijack our session IDs through the access of session ID tokens. 

Besides, sessions and local storage data can be stolen in similar ways as well. That’s why it is recommended not to store confidential information such as tokens in the browser unless certain web development architecture dictates to do so. 

8) Indicating Users To Perform Wrong Actions

Remember the Cross-site Request Forgery exploitation we discussed a little earlier? At this point, you need to understand that hackers gain access to unauthorized modules even when you are not online or in a session. This means that even if your website or application is not open, hackers could still be gaining access to authorized pages. This can happen to all cookie-based sessions through the request of authorization cookies. 

Besides, it is also possible for hackers to publish their own web pages and force them to perform malicious activities or requests to other websites in the background (in stealth) when a user opens it. Through links posted on forums, social media platforms and suspicious websites, browsers can be made to call or access other websites with the help of cookies. 

To prevent this, you could deploy a tokenization mechanism, where all client-server communications require an additional security token for data transmission. This token resides nowhere - not even in cookies. Every form should have a token generated for it and sent to the server for every single request as the user is still active on that particular website. 

Wrapping Up

So, these were some of the lethal vulnerabilities and JavaScript security practices. Now that you are familiar with possible avenues where things can go wrong, ensure these loopholes are fixed or patched when you work on your next JavaScript project. If you’re working on one currently, revisit the aspects and implement whatever we discussed so far. 

It’s always the minutest of the details that lead to colossal damages. Let’s build a safer internet for everyone out there. 

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Published on May 19, 2021
Patrick R
Written by Patrick R
A techno-commercial leader heading Intuz as Director of Growth With over 12 years of experience in the field of Information Technology. His experience and expertise will entice developers and business entrepreneurs with rich content on the latest technology stack.


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