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 lead to 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. His work deepened the technical understanding of replay-prevention within the OpenID4VCI specification, contributing to a more robust and secure implementation for future development.