Which situation is of most concern to an IS auditor during a post-implementation review when code was erroneously included in a production release?

The situation that raises the most concern during a post-implementation review is when the change did not have change management approval. This is critical because the absence of proper change management processes means that there was no oversight to evaluate the impact, risks, or necessity of the code prior to its deployment. Change management serves as a safeguard to ensure that modifications to the system are planned, approved, and documented, reducing the risk of introducing errors or security vulnerabilities into the production environment.

In this case, the lack of change management approval not only exposes the organization to potential operational risks but also raises questions about compliance with internal policies and external regulations. It could indicate a breakdown in the established procedures designed to ensure quality and stability in software releases.

The other situations, while concerning, do not reflect as severe a breach of process. If the code was merely missed during the initial implementation, it suggests a lapse in the development process but does not inherently imply a lack of controls. Discovering the error during the review indicates that the review process is functioning to some degree, allowing for errors to be identified, albeit late in the process. Lastly, the use of the same change order number might suggest issues with documentation practices, but it does not directly indicate a failure in the change management