Niels van Dijk enhanced the OpenID4VCI repository by improving its documentation to clarify the risks and prevention mechanisms associated with replay attacks in the Pre-Authorized Code Flow. He focused on detailing how vulnerabilities such as shoulder surfing and the sharing of QR codes or links could enable unauthorized access, directly addressing gaps identified in issue #23. Using Markdown and leveraging his documentation skills, Niels provided explicit distinctions between different replay attack variants and outlined mitigation strategies in alignment with the OpenID4VCI specification. His work deepened the technical understanding of replay prevention, contributing to a more robust security posture for the project.