Worked on the openid/OpenID4VCI repository to enhance the clarity and security of its documentation, specifically addressing replay attack vulnerabilities in the Pre-Authorized Code Flow. Focused on detailing how threats such as shoulder surfing and the sharing of QR codes or links can lead to unauthorized access, the work aligned closely with the OpenID4VCI specification and addressed gaps identified in issue #23. Used Markdown to structure comprehensive documentation updates, emphasizing both the identification of replay attack variants and the mechanisms for their prevention. The contribution improved the overall understanding of security risks and mitigation strategies within the OpenID4VCI ecosystem.