Why does the “Unknown Publisher” message appear during the uninstall of a digitally signed package?
When a package is installed, Windows caches the MSI by placing it in the Windows\installer folder. During this process, all the unnecessary information (including the digital signature) is removed in order to decrease the size of the file. When an uninstall is launched from “Add or Remove programs” or through the Uninstall shortcut, Windows Installer uses the cached MSI. Since this file doesn’t have a digital signature, the “Unknown Publisher” message will be showed. A solution for this is to make sure the user can uninstall the package only by launching the original file.
