How to improve prevent XSS for a one-page website

Question

Accepted Answer

To significantly improve XSS prevention for a one-page website, prioritize robust input validation on the server-side, ensuring all user-supplied data conforms to expected formats and types. Crucially, implement context-aware output encoding for any dynamic content rendered to the DOM, escaping special characters like , ", ', and & before display to neutralize malicious scripts. A strong Content Security Policy (CSP) header should be deployed to restrict resource loading, specifying trusted sources for scripts, styles, and other assets to prevent injection of unauthorized content. Furthermore, leverage modern frameworks and libraries that often incorporate built-in XSS defenses, and always use HTTP-only cookies for session management to prevent script access. Always sanitize or escape any data received from APIs before injecting it into the HTML structure client-side, making sure all rendering paths are secure.