Besides Cloudflare, what other measures should developers take to prevent XSS even if Cloudflare is in place?

Developers must implement robust server-side and client-side XSS prevention measures, as Cloudflare is a layer of defense, not a complete solution. Key measures include: 1. Input Validation: Strict validation and sanitization of all user-supplied input. 2. Output Encoding: Context-specific output encoding of all untrusted data before rendering it in HTML, JavaScript, CSS, or URL contexts. 3. Content Security Policy (CSP): Implementing a strong CSP to restrict allowed sources for scripts, styles, and other resources. 4. HTTP-only cookies: Using the `HttpOnly` flag for cookies to prevent client-side scripts from accessing them. 5. Secure Headers: Using `X-XSS-Protection` (though deprecated, still used), `X-Content-Type-Options`. 6. Framework Security: Leveraging built-in XSS protection features of modern web frameworks.