Known Issue Rollback (KIR) is a Microsoft Windows feature designed to quickly revert specific problematic updates that cause widespread issues. When a Windows update introduces a bug or breaks functionality for many users, Microsoft can deploy a KIR to automatically undo only the problematic part of the update, restoring affected systems to their previous working state. This process is managed centrally by Microsoft and does not require manual intervention from end users or IT administrators. KIR helps minimize downtime and disruption by swiftly addressing critical issues while allowing unaffected parts of the update to remain in place, ensuring both security and stability.