JavaScript Security: Vulnerabilities and Best Practices

JavaScript is among the core coding languages in web development. The language is primarily used to create interactive and dynamic web pages. The widespread use of the language makes it prone to cyber threats. In this article, we are going to talk about the inherent vulnerabilities in JavaScript and the JavaScript Security best practices to bolster code security against any breaches.

Understanding the Priority of Securing JavaScript

JavaScript being a front-end language, most of its applications are susceptible to breaches due to the application’s code being readily available to users. Cyber attackers can easily pinpoint the weakness of your application code effortlessly.

With readily accessible code, an attacker can modify your code within the browsers or aim at the server-side applications allowing them to circumvent front-end defenses.

How Does JavaScript Security Function?

The absence of compilation leaves the source code exposed, posing security threats. This however lets the applications be analyzed easily by static application security testing (SAST).

By analyzing the application’s source code, the SAST tools can easily detect any known threats and potential concerns with the applications.

Embedding JavaScript security scans into automated DevOps workflows guarantees the detection and resolution of any vital threats before code is committed to a repository.

Common JavaScript Vulnerabilities

  1. Cross-Site Scripting (XSS) 

Cross-site scripting, often abbreviated as XSS, is a type of attack where someone implants harmful code into a reputable website or application. When the rogue code is executed in a user’s browser, it can access their data, like cookies or session IDs. With this information, the attacker can impersonate users or redirect them to harmful websites that are under the attacker’s control

Cross-Site Scripting Example
Imagine a scenario where a perpetrator discovers a flaw within an e-commerce site. The cyber intruders embed harmful code into specific product pages. Now when online buyers click on these manipulated listings, they are redirected to a false login page. If a user unknowingly logs in, the perpetrators gain access to their email and password information. The attackers can now pose as the users and login to the e-commerce site as impersonators, they can also gain sensitive details like credit card information. This example is based on a real attack that affected eBay in 2014.

  1. Cross-Site Request Forgery (CSRF): 

This type of vulnerability enables attackers to coax users into executing actions they hadn’t planned. This attack provides a loophole where attackers bypass the same origin policy—a protective measure that prevents various websites from interfering with each other. For instance this could involve altering a victim’s account details such as email, or password credentials. With this action the perpetrator could easily gain full control of the user’s account and if the compromised user has high-level permissions in the application, the attacker might assume full control over all application functions.

  1. Poor Input Validation:

Poor input validation constitutes a security vulnerability, where an application neglects to thoroughly inspect or sanitize incoming data prior to processing. This flaw enables cyber intruders to introduce malicious input which can potentially compromise system integrity or acquire sensitive data. It’s one of the most pressing security issues that affect applications across different domains including web, desktop and mobile applications. 

JavaScript Security Best Practices

  1. Secure Coding Practices

Often referred to as secure programming, it involves crafting code in a high-level language. Its main aim is to thwart potential threats that might compromise data integrity or disrupt targeted systems. To fully adopt these practices, it’s important to establish a secure development ecosystem. Such a system should have a robust IT infrastructure that is supported by secure hardware and software and services that are offered by reputable providers.

  1. Use of JavaScript Linter

Linting your code is possibly the simplest way to avoid JavaScript security issues in your code. Linting code is a process of using automated tools to check your source code for both logical and stylistic errors. The most common JavaScript linters are JSLint, JSHint and ESLint.

  1. Have an SSL Certificate on your Website

To properly safeguard your website or team portal it is vital to include an SSL certificate to your site. An SSL is a certificate that acts as a shield that encrypts all information between servers and users. This helps in securing sensitive information. If your website or team portal lacks an SSL, there are several providers that you can get an SSL certificate from. You can get cheap wildcard SSL, multi-domain SSL, OV SSL, etc. as per your website’s requirements.  

  1. Validate User Input 

Verifying user input integrity is among the most important measures to prevent any security threat like injecting harmful code to a website. HTML5 attributes such as ‘required,’ ‘max,’ ‘min,’ and ‘type,’ offer pre-built validation capabilities. This allows immediate basic checks without requiring client-side scripting. Modern browsers such as Chrome and Opera, support Constraint Validation API which empowers developers to create personalized validation scripts using JavaScript.

  1. Use of escape or Encode user input

If you are to safeguard your website from an XXS threat, you need to handle any incoming data through escaping or encoding techniques. This method alters potentially hazardous characters into safe representations. For instance, adding a backslash (\) before a quotation or replacing ‘<’ with the &gt’ in HTML. This prevents unwanted code execution. Using this tactic can prevent threats that cyber intruders pose on online websites and applications.


In today’s world, it’s important to make sure that your JavaScript code is secure. Knowledge of cyber security threats is paramount to every developer. By implementing the above JavaScript Security best practices, developers can reduce the risk of cyber-attacks and protect sensitive data. It’s important to always have continual vigilance and adherence to security best practices, this safeguards your applications and websites while maintaining user trust.

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