Dominik Kundel discusses enhancing the security of Express applications, a popular Node.js web server framework, by implementing best practices and using middleware such as Helmet and Express-CSP-Header. Express, while flexible and easy to use, doesn't automatically follow security best practices, but the addition of Helmet can significantly improve security by adding HTTP headers that protect against vulnerabilities. These headers include X-DNS-Prefetch-Control, X-Frame-Options, Strict-Transport-Security, X-Download-Options, X-Content-Type-Options, and X-XSS-Protection, each serving a specific security purpose like preventing MIME sniffing or cross-site scripting (XSS) attacks. Additionally, setting up a Content Security Policy (CSP) can further safeguard applications by controlling resource loading and blocking unwanted code execution. The article emphasizes the importance of staying vigilant about web security and provides resources for further learning, including securityheaders.io and the Open Web Applications Security Project (OWASP).