Securing dangerouslySetInnerHTML in React and Next.js

React escaping logic automatically neutralizes standard Cross-Site Scripting (XSS) vectors inside curly braces {userContent}. However, developers often bypass this default protection using dangerouslySetInnerHTML when rendering blog content or rich text emails.

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The Cross-Site Scripting Risk

If you bind unvalidated inputs directly to dangerouslySetInnerHTML, an attacker can execute malicious scripts inside user browsers.

// VULNERABLE CODE
const unsafeHTML = `<img src="x" onerror="alert(document.cookie)" />`;
return <div dangerouslySetInnerHTML={{ __html: unsafeHTML }} />;

When this component mounts, the browser attempts to render the broken image, fires the onerror event, and executes the arbitrary script.

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Safe Sanitization Standards

1. Use DOMPurify

Never render raw HTML without sanitizing it first. Install and use a battle-tested library like DOMPurify (for Node/Vite) or isomorphic-dompurify (for Next.js SSR):

import DOMPurify from "isomorphic-dompurify";

const CleanHTML = ({ unsafeHTML }) => {
  const cleanHTML = DOMPurify.sanitize(unsafeHTML);
  return <div dangerouslySetInnerHTML={{ __html: cleanHTML }} />;
};

2. Configure Content Security Policy (CSP) Headers

Implement strict Content Security Policy headers to disable inline scripts and enforce trusted domain origins.