JWT and web security

---

---

When saving JWT tokens, the best storage method depends on your security requirements and the type of token (access vs. refresh):

Best Practices for Storing JWT Tokens

1. Access Tokens (Short-lived)

• Best Option: Memory (React State, Redux, etc.)
  • Store the token in memory (e.g., React state, Redux, or a variable).
  • Prevents Cross-Site Scripting (XSS) attacks.
  • Downside: The token is lost on page refresh.
• Alternative: HttpOnly Cookies
  • More secure but requires backend support.
  • Automatically included in requests to the same domain.
  • Prevents XSS attacks but vulnerable to Cross-Site Request Forgery (CSRF).

2. Refresh Tokens (Long-lived)

• Best Option: HttpOnly Secure Cookies
  • Cannot be accessed via JavaScript, preventing XSS.
  • Must be refreshed via an endpoint that checks the token.
  • Use SameSite=Strict to mitigate CSRF attacks.
• Avoid: Local Storage & Session Storage
  • Vulnerable to XSS attacks. If an attacker injects JavaScript, they can steal the token.

Recommended Approach

1. Store access tokens in memory.
2. Store refresh tokens in HttpOnly Secure Cookies.
3. Use the refresh token to obtain a new access token when needed.

Would you like guidance on implementing this in your React or Node.js app?

---

When using MSAL for React (@azure/msal-react), JWT tokens (ID token, access token, and refresh token equivalents) are stored based on the configured cache location in MSAL Configuration. The storage options are:

Where MSAL Saves JWT Tokens?

MSAL uses cacheLocation in its configuration to determine where it stores tokens:

• Local Storage (localStorage)
• Session Storage (sessionStorage)
• Memory ("sessionStorage" by default)

Default Behavior

By default, MSAL stores tokens in sessionStorage, meaning:

• The tokens are cleared when the user closes the browser.
• The tokens are available only within the same session.

How to Configure Storage in MSAL?

You can specify where to store tokens in the cache configuration:

import { PublicClientApplication } from "@azure/msal-browser"
 
const msalConfig = {
  auth: {
    clientId: "YOUR_CLIENT_ID",
    authority: "https://login.microsoftonline.com/YOUR_TENANT_ID",
    redirectUri: "/",
  },
  cache: {
    cacheLocation: "localStorage", // or "sessionStorage"
    storeAuthStateInCookie: true, // Helps in certain browsers (IE11, Safari)
  },
}
 
const msalInstance = new PublicClientApplication(msalConfig)

Storage Options & Security Considerations

Storage Type	Persistence	Security	Use Case
sessionStorage (default)	Cleared on browser close	Less risk of XSS attacks	Recommended for security
localStorage	Persists after browser close	Vulnerable to XSS	Use only if session persistence is required
Memory (Custom implementation)	Cleared on page refresh	Most secure, prevents XSS	Requires custom handling

How to Clear Tokens?

To remove the tokens:

msalInstance.logoutRedirect() // Logs out & clears tokens
msalInstance.logoutPopup() // Logs out using a popup

Would you like help handling token expiration or silent authentication in your React app?