Securing Web Storage in JavaScript: Best Practices for Handling Sensitive Data

Securing Web Storage in JavaScript: Best Practices for Handling Sensitive Data

Web storage in JavaScript has become an integral part of most modern web applications. It provides a way for web applications to store data persistently in the browser. While this definitely increases the functionality and convenience of web applications, it also creates an avenue for potential security risks. Hence, it becomes pivotal to understand how to secure web storage in JavaScript and handle sensitive data effectively.

Understanding Web Storage

Web storage in JavaScript is provided in the form of two objects: localStorage and sessionStorage. Both of these provide a way to store key-value pairs in a web browser. While localStorage persists even when the browser is closed and reopened, sessionStorage gets cleared once the session ends, i.e., when the browser is closed.

Here is a simple example of how to use localStorage:

localStorage.setItem('name', 'codedamn'); console.log(localStorage.getItem('name')); // codedamn

While web storage is convenient and easy to use, it is important to remember that it is not designed to store sensitive information like user passwords or credit card numbers. Let's look at the best practices to secure web storage.

Best Practices for Handling Sensitive Data in Web Storage

Avoid Storing Sensitive Data

As a rule of thumb, you should avoid storing sensitive information in web storage. This includes data like user passwords, credit card numbers, and other personally identifiable information (PII). Even though web storage data is only accessible by the same origin (same domain, protocol, and port), there are ways that this data can be accessed through cross-site scripting (XSS) attacks.

Always Sanitize Inputs

One of the most common web vulnerabilities is Cross-Site Scripting (XSS). In simple terms, XSS attacks happen when an attacker manages to inject malicious scripts into web pages viewed by other users. Sanitizing inputs is a common way to prevent XSS attacks. Sanitizing means stripping out or escaping characters that have special meaning in HTML.

const sanitizeHTML = (str) => { return str.replace(/[^\w. ]/gi, (c) => `&#${c.charCodeAt(0)};`); }


When you're dealing with sensitive data, it's important to ensure that the data is transmitted securely over the network. HTTPS (Hypertext Transfer Protocol Secure) is a secure version of HTTP, where the communication between the client and the server is encrypted.

Data Encryption

If you have to store sensitive data in web storage, ensure it is encrypted. Data encryption translates data into another form, or code, so that only people with access to a secret key (formally referred to as a decryption key) or password can read it.

// using the CryptoJS library for AES encryption let encryptedData = CryptoJS.AES.encrypt(data, secretKey); localStorage.setItem('data', encryptedData);

This way, even if the data is accessed, it will be in an unreadable format, thereby protecting the information.

Use HTTP Only Cookies

If you need to store sensitive data for any reason, HTTP only cookies can be a more secure option. These cookies cannot be accessed through JavaScript, which provides protection against XSS attacks.

// Setting an HTTP Only cookie res.cookie('token', '123456', { httpOnly: true });

Remember, no security measure is 100% foolproof, but these best practices will significantly reduce the risk of your web storage being compromised.

Frequently Asked Questions (FAQ)

1. Is it safe to store JWTs (JSON Web Tokens) in web storage?

While it's possible to store JWTs in web storage, it's generally not recommended due to the risk of XSS attacks. A safer place would be an HTTP Only cookie.

2. Can web storage be viewed by users?

Yes, a user can view their own web storage through their browser's developer tools. However, they cannot view the web storage of others.

3. What is the storage limit of web storage?

Most modern browsers provide a limit of about 5-10MB per origin.

4. Can web storage data persist across multiple windows?

Yes, localStorage persists across multiple windows and even after the browser is closed and reopened. However, sessionStorage is limited to the session and does not persist across windows or after the browser is closed.

Remember, security isn't a one-and-done deal. It's a continuous process of learning, adapting, and improving. As you continue your journey in web development on codedamn, keep these best practices in mind to create not only functional but also secure web applications.

For additional information on web storage, you can refer to the official MDN documentation. Similarly, for a deeper understanding of XSS attacks, the OWASP website provides a comprehensive guide.

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