React Security Patterns Every Developer Should Know

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}} /> 

Instead, sanitize with a trusted library:

import DOMPurify from 'dompurify'; const safeBio = DOMPurify.sanitize(user.bio); <div dangerouslySetInnerHTML={{__html: safeBio}} /> 

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) }); 

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> 

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'" ); 

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