When Microsoft re-releases a security update or a hotfix, the registry entries are not updated. This behavior is expected. This behavior does not affect the system on which the security update or the hotfix is installed.

Consider the following scenario. An earlier version of a security update or a hotfix is installed on the computer. You install a new version of the security update or the hotfix. The FileList key in the registry for the security update or the hotfix still displays the earlier file versions and checksums.

The security update installer or the hotfix installer treats the new installation like a reinstallation. Therefore, the security update installer or the hotfix installer does not update the registry entries.

Microsoft Windows Update and Microsoft Baseline Security Analyzer (MBSA) do not use the registry entries to look for installed fixes. Any tools that use the registry entries assume that the installed file version is the version that is listed in the registry or a newer version. Therefore, you do not break any reporting tools or any detection tools when you install a new version of a security update or a hotfix.