5 JavaScript Security Best Practices for 2024

Cybersecurity has become an ever-changing battlefield, with the security of JavaScript applications no exception. Web applications have become a common target for hackers in an attempt to gain access to sensitive data and financial details, emphasizing the importance of JavaScript web app security in 2024.

This piece will explore the latest JavaScript best practices in 2024, addressing the most common vulnerabilities and how they can be mitigated. Amongst other things, we’re tackling securing APIs, preventing cross-site scripting (XSS) attacks, and implementing content security policies (CSP).

Additionally, we will also assess the latest security tools and techniques that help developers safeguard their JavaScript applications against modern threats.

Common JavaScript Security Vulnerabilities in 2024

JavaScript (JS) applications can be targeted by cybercriminals in many ways, in particular by exploiting client-side execution of JS with a range of tactics and techniques. Let’s quickly recap some of the most common JavaScript vulnerabilities that need to be protected against in 2024.

• Cross-site scripting (XSS): Malicious scripts are injected into a vulnerable application or website, allowing hackers to manipulate what is returned by the web browser.
• Man-in-the-middle attacks (MitM): A general term for an attack that involves a hacker positioning themselves between an application and the user to obtain sensitive data.
• Denial of service attacks (DoS): An attack that floods a server with countless requests to take an application offline.
• Cross-site request forgery (CSRF): A malicious exploit that tricks an authorized user into performing an unintended action, such as submitting a financial transaction.
  Session hijacking: A hacker may use a range of techniques to steal a user’s unique session ID, enabling them to hijack an active session.

Current JavaScript Security Best Practices

JavaScript developers need to have full awareness of cybersecurity vulnerabilities when building applications. That’s because, fundamentally, JavaScript was not designed with security in mind — meaning hackers can easily input malicious scripts. This issue is compounded further with the use of various third-party libraries and frameworks that increase the attack surface of an application.

Below we outline five security best practices in 2024 that all developers need to integrate into their JavaScript development process. From regular auditing to input sanitization, abiding by security-by-design principles during all stages of development is essential to minimize vulnerabilities and ensure a quick resolution to any threats.

1. Securing APIs

Many APIs are built within Node.js, the leading JavaScript runtime, typically using representational state transfer (REST) architecture. There are several key considerations when securing REST APIs in Node.js:

• Always use HTTPS for all APIs, to prevent unauthorized access to data.
• Use access control lists (ACLs) to restrict access to only authorized users.
• Implement authentication methods to prevent unauthorized access. Using an API key is the most common form of authentication, but Node.js also supports other methods, such as OAuth and JWT.
• Configure input validation to prevent malicious or incorrect data from being sent to the API.

2. Implementing Content Security Policies (CSP)

Any JavaScript web application needs to have a Content Security Policy (CSP), a browser security standard that dictates what the browser is allowed to load — whether that be a domain, subdomain, or resource. Without a CSP, hackers can exploit cross-site scripting vulnerabilities, potentially resulting in a data breach.

To enable a CSP, applications and websites need to have a CSP header or use a CSP meta-tag, telling the browser what it is allowed to load. Meanwhile, CSP directives provide further control, stating which domains are allowed to load specific types of resources.

Note: Before any domains can be assigned to CSP directives, you should be aware of and inventory each resource type that is loaded by every domain, to avoid any loss of functionality.

3. Input Sanitization

In JavaScript, input sanitization refers to cleaning and validating any data that is input by the user, including checking for formatting issues. This avoids input errors, while also removing any malicious code before it can be executed. As well as enhancing security, input sanitization also improves the performance and usability of applications, while significantly reducing the amount of time spent debugging input errors, ensuring that input data is always valid.

The most common form of input sanitization in JavaScript is escaping user input, a process that reduces the chance of malicious inputs — such as the scripts used to initiate XSS attacks. Escape user input involves encoding special characters that could be used incorrectly or maliciously.

4. Preventing Cross-Site Scripting (XSS) Attacks

As well as sanitizing user input and implementing content security policies, XSS attacks can be prevented by validating and encoding input, in addition to using HTTP-Only Cookies. Validating user input ensures that only allowed characters are being used before data is displayed on the page. Additionally, encoding input converts any special characters into HTML entities that a web browser cannot execute — adding an extra layer of security.

The use of HTTP-only cookies is also recommended as these cookies can only be accessed by the web server and not by the client-side JavaScript code. Thus, preventing hackers from injecting malicious code.

5. Regular Security Audits

Conducting regular security audits is crucial for identifying potential vulnerabilities in your JavaScript applications. This extends to digital asset management systems, where regular audits ensure that assets are properly secured and managed, reducing the risk of unauthorized access.

A typical JavaScript security audit will likely consist of the following steps:

1. Check dependencies, which can be kept updated by using tools such as Dependabot to receive notifications of when new versions or security patches are available.
2. Ensure input validation and sanitization are correct.
3. Make sure no environment variables or components are exposed client-side.
4. Confirm that all security headers have been implemented. In addition to CSP, your application should also contain Strict-Transport-Security (HSTS), X-Content-Type-Options, Permissions-Policy, and Referrer-Policy headers.
5. Verify that all key functions are centralized, to avoid inconsistencies and to optimize testing, auditing and maintenance.
6. Use the built-in code editor security tools, such as linting and static analysis, to highlight potential security issues.

Security Tools JavaScript Developers Need To Know

Adhering to best practices when developing JavaScript applications is difficult, if not impossible, without the right tools and techniques. Here are a few of our favorite web application security tools in 2024.

Snyk

This developer-first security platform can automatically identify vulnerabilities within JavaScript code, dependencies, and containers. Accessing its own security database and using logic programming rules in real-time, Snyk can highlight any vulnerabilities as they are coded.

Zed Attack Proxy (ZAP) by OWASP

Zed Attack Proxy (ZAP) is an open source penetration testing tool for web applications, supporting both automated and manual testing. Favored for its ease of use and accessibility for varying skill levels, ZAP is an ideal development tool to highlight security issues.

ZAP’s heads-up display (HUD) user interface can be overlaid on a web application, allowing developers to conduct live testing within a web browser. The ZAP marketplace also offers an extensive range of add-ons to further increase the functionality of the tool.

ZAP is an open source solution and promises to help control security costs and make large-scale projects more viable.

Cypress Testing Framework

Cypress is often preferred to JavaScript testing frameworks such as Selenium due to its fast execution, reliability, real-time processing, visual debugging capabilities, and API testing features. Its simplicity makes it extremely popular with developers, enabling them to create bespoke security tests that can be automatically run as part of a Continuous integration (CI) methodology.

Conclusion

Web applications that are coded in JavaScript may contain an array of vulnerabilities that may be missed if a developer does not adhere to security processes and best practices.

Best practices include implementing API security, Content Security Policies (CSP), and input sanitization, while attacks such as Cross-Site Scripting (XSS) can be prevented by ensuring input data is validated and encoded.

For an effective JavaScript security strategy, developers must also conduct regular audits that check each aspect of an application that could present a security risk.