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React Security Patterns Every Developer Should Know

#react #security #webdev #javascript

Building secure React applications requires more than just following best practices—it demands understanding the specific vulnerabilities that single-page applications face and implementing defensive patterns from the start.

1. Prevent Cross-Site Scripting (XSS)

By default, React escapes values in JSX. But shortcuts like dangerouslySetInnerHTML open the door to attackers:

// Vulnerable
<div dangerouslySetInnerHTML={{__html: user.bio}} />
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Instead, sanitize with a trusted library:

import DOMPurify from 'dompurify';
const safeBio = DOMPurify.sanitize(user.bio);

<div dangerouslySetInnerHTML={{__html: safeBio}} />
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2. Treat Authentication as Sacred

Tokens in localStorage are exposed to XSS. A safer pattern is httpOnly cookies with CSRF tokens:

await fetch('/api/login', {
  method: 'POST',
  credentials: 'include',
  headers: {
    'Content-Type': 'application/json',
    'X-CSRF-Token': await getCSRFToken()
  },
  body: JSON.stringify(credentials)
});
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3. Sanitize Props and Inputs

Props aren’t immune. Always validate and sanitize before rendering:

const cleanQuery = query.replace(/[<>]/g, '');
<h2>Results for: {cleanQuery}</h2>
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4. Keep State Lean

Context and Redux should not carry secrets. Expose only what the UI truly needs (permissions, IDs, roles).

5. Respect Environment Configurations

Anything prefixed with REACT_APP_ is visible to the client. Keep true secrets server-side, delivered through a secure API.

6. Secure Headers at Deployment

Defend React apps at the edge by setting strict headers:

res.setHeader('Strict-Transport-Security', 'max-age=31536000');
res.setHeader('Content-Security-Policy',
  "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"
);
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Security isn’t a feature; it’s a foundation.

When baked into your React components and architecture, these patterns create user trust that lasts.

Looking for a partner who builds React apps with security at the core?

See how I help teams deliver resilient frontends: kodex.studio

Top comments (1)

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ariansj profile image
Arian Seyedi •

Absolutely spot on!
I’ve faced similar challenges, especially with XSS vulnerabilities when rendering user-generated content. Using DOMPurify saved me from a lot of headaches.

Another thing I’ve found useful is keeping state minimal , never store sensitive info in Redux or Context; just the info needed for the UI. It’s crazy how many people overlook that in SPAs.

how do you handle refresh tokens securely in client-heavy React apps? Do you lean fully on httpOnly cookies or a hybrid approach?