JavaScript Security in 2023: The Complete Guide to Stay Secure

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The importance of JavaScript security has never been greater. JavaScript continues to dominate the web development landscape, powering a significant majority of websites and web applications. However, this widespread adoption also makes it an attractive target for cybercriminals. In this article, we will explore the key risks associated with JavaScript security and explore how security measures, including Reflectiz, can help your business keep its web applications running safely and securely in 2023.

What is JavaScript?

More than 67% of professional developers use JavaScript and it works ‘under the hood’ on more than 95% of all websites. It’s so popular because it’s such a powerful programming language. It’s ideal for creating interactive and dynamic web applications, but it’s this power and widespread use that also makes it such a prime target for attackers. Oh, and let’s not forget that it’s been counted among the most vulnerable languages, along with C, C++, Java, PHP, and Python. (Poor JS. Some people give it such a hard time…)


Specific JavaScript Security Risks

Here are some of the compromises that attackers will try to inflict on you via JavaScript:

Cross-site scripting (XSS): lets attackers inject malicious code into a web page. This can then be executed by the victim’s browser, potentially stealing their cookies or other sensitive information.

Malware injections. These involve the insertion of malicious code into a website to infect the user’s computers with malware. This can lead to data theft, system corruption, and financial losses.


Clickjacking is a technique they will employ to deceive users into clicking hidden buttons or links on websites, resulting in unintended actions such as money transfers or revealing personal information.

Man-in-the-Middle (MITM) attacks: occur when an attacker intercepts communications between a user’s browser and a web server, and JavaScript is vulnerable to them because it can be executed on the client side, in the user’s browser. Once underway, the attacker can read, modify, or inject code to steal data or compromise the system.

Session hijacking: attackers steal a user’s session cookie, which can then be used to impersonate the user, potentially allowing the attacker to access their account or data.

What Does JavaScript Security Involve?

Certain programming practices, design flaws, and security considerations can make JavaScript code susceptible to vulnerabilities. Here are a few reasons why using JavaScript can open up vulnerabilities:


Client-Side Execution: JavaScript is primarily executed on the client side, meaning it runs within the user’s web browser. This makes it easier for attackers to manipulate or tamper with the code since it is accessible to anyone who can view the webpage source. This makes it important to validate and sanitize any user inputs to stop attacks like cross-site scripting (XSS).

Lack of Type Safety: JavaScript is a dynamically typed language, meaning variables can change their type during runtime. This flexibility can lead to coding errors and vulnerabilities. If proper input validation and type checking are not implemented, it can result in security issues like type confusion or unexpected behavior.

Cross-Origin Resource Sharing (CORS): JavaScript sticks to the Same-Origin Policy, which doesn’t allow web pages to make requests to different domains. However, CORS permits controlled access to resources on other domains. Misconfigurations in CORS settings can lead to cross-origin attacks, such as cross-site request forgery (CSRF), where an attacker tricks a user into carrying out certain actions on a trusted website.

Dependency Management: JavaScript relies heavily on external libraries and frameworks. If these dependencies are not carefully managed, outdated or vulnerable versions can be used, introducing security risks. That’s why it’s crucial to keep dependencies up to date and apply security patches without delay.

Insecure Direct Object References: JavaScript code may expose direct references to sensitive data, such as database identifiers or file paths. If these references are not properly protected or validated, an attacker may be able to manipulate or access unauthorized data.

Client-Side Validation: JavaScript often performs client-side form validation for user input. However, relying solely on client-side validation can be dangerous, as it can be bypassed by malicious users. Server-side validation should always be implemented as an additional layer of defense.

How to Stay Safe

Use a secure development process: This includes following secure coding practices, such as input validation.

Use a content security policy (CSP): A content security policy that can be used to limit the kinds of resources that a web page can load. This can help to prevent XSS attacks.

Implement proper access controls: Requires users to authenticate themselves before accessing sensitive functionality or data. Use a secure authentication mechanism such as username/password, tokens, or OAuth. Once authenticated, implement authorization checks to determine if the user has the necessary permissions to perform specific actions or access certain resources.

Use secure development practices: Organizations should adopt secure development practices, such as code reviews, penetration testing (simulated real-world attacks on a system to identify vulnerabilities and potential security weaknesses.), and unit testing (testing individual components or units of code in isolation to ensure that they behave as expected), to help keep sites and web applications safe.

Use a web application firewall (WAF): A WAF can help to protect web applications from common attacks, such as SQL injection.

Keep software up to date: Including JavaScript libraries and frameworks. This will help to ensure that known vulnerabilities are patched.


How Reflectiz can assist

Reflectiz provides a comprehensive security platform to help businesses of all sizes protect their web applications from JavaScript-based attacks. Here are the various ways it achieves comprehensive protection:

Real-time Monitoring

Reflectiz monitors all third-party scripts and applications on your website in real time, enabling you to identify vulnerabilities very quickly.

Inventory and Dependency Analysis

Reflectiz creates a complete inventory of third-party applications and scripts on your website, analyzing their dependencies to identify potential vulnerabilities.

Risk Assessment

Reflectiz employs advanced algorithms to analyze the security risks associated with each third-party script and application, allowing you to prioritize your security efforts effectively.

Incident Response

Reflectiz offers incident response capabilities, including automatic alerts, real-time threat intelligence, and access to a team of security experts to help mitigate potential threats.

Compliance Monitoring

Reflectiz ensures compliance with industry regulations like GDPR and HIPAA, giving you complete peace of mind about website security and compliance.


Reflectiz gives you visibility into third-party scripts and their behaviors, which is crucial for identifying vulnerabilities and unauthorized access attempts.

As we noted, JavaScript code can be modified on the client side, making it challenging to monitor and control execution. Attackers exploit this flexibility to inject malicious code or manipulate existing scripts, so proper visibility is essential for detecting and mitigating such attacks.

Websites consist of interconnected components, including JavaScript files, APIs, and plugins. Understanding these components and their relationships is vital for identifying security risks. Blind spots can lead to unnoticed vulnerabilities, which attackers can exploit, so the complete oversight offered by the Reflectiz dashboard is a real game changer.


The Reflectiz platform gives your organization complete visibility and control over JavaScript security. The platform offers deep insights into the web ecosystem, mapping all third-party scripts, open-source tools, and external domains. This level of visibility helps you understand your JavaScript usage, identify vulnerabilities, and take proactive measures to secure your websites.

With Reflectiz’s intuitive dashboard, security teams can effectively monitor and manage all JavaScript components. Real-time updates alert users to changes that affect security, and by gaining a comprehensive overview of JavaScript elements’ behaviors and interactions, you can detect and mitigate threats early on, reducing the risk of data breaches and unauthorized access.

So, while JavaScript security poses challenges due to its extensive use of third-party scripts, its dynamic nature, and the complexity of the web ecosystem, Reflectiz’s comprehensive visibility and control solution empowers you to overcome these (and many other) challenges.

Book a demo today and discover how your organization can benefit from all the advantages of JavaScript without compromising your website security. 

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