Intermediate LevelExpress JS
How does Helmet.js secure Express applications by setting HTTP security headers?
❓ Interview Prompt: Explain critical HTTP security headers set by Helmet (CSP, HSTS, X-Frame-Options, X-Content-Type-Options) and how they mitigate attacks.
Helmet.js is an essential Express middleware that automatically sets 15+ secure HTTP response headers to defend against common web vulnerabilities.
Key Security Headers Configured by Helmet:
1
'Content-Security-Policy' (CSP): Restricts where scripts, styles, and images can be loaded from, blocking unauthorized external CDNs or inline scripts (XSS defense).
2
'Strict-Transport-Security' (HSTS): Tells browsers to always connect to your server over HTTPS, preventing SSL stripping attacks.
3
'X-Frame-Options: DENY / SAMEORIGIN': Prevents your site from being embedded inside an '<iframe>', defeating Clickjacking attacks.
4
'X-Content-Type-Options: nosniff': Stops browsers from MIME-sniffing content types.
5
'X-Powered-By' (Removal): Helmet removes the default 'X-Powered-By: Express' header.
Code Implementation Example
javascript
import express from 'express';
import helmet from 'helmet';
const app = express();
// Secure Express with Helmet custom Content Security Policy and HSTS
app.use(helmet({
contentSecurityPolicy: {
directives: {
defaultSrc: ["'self'"],
scriptSrc: ["'self'", "https://trusted-cdn.com"],
styleSrc: ["'self'", "'unsafe-inline'"],
imgSrc: ["'self'", "data:"]
}
},
hsts: { maxAge: 31536000, includeSubDomains: true }
}));💡Securing an Express server with Helmet.js custom Content Security Policy and HSTS.
🎯 Interview Key Takeaway
Always use Helmet.js as the first middleware in Express to set critical security headers like CSP, HSTS, and X-Frame-Options.
#Helmet.js#Security#Headers#Intermediate
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