Unverified ownership in the Windows installer of Progressive Robot hMailServer 6.3.7 allows a local authenticated user to run code as the mail server's service account or as an administrator when setup installs into, or upgrades, a program folder that accounts other than the administrators could write before, such as one made beforehand at the root of a drive. 6.3.7 fixed CVE-2026-107571 by giving the program folder, Bin and ControlPanel permissions that only administrators may change, but setup refused nothing that was already in them, or in the folders that hold the event script, the add-ons and the database scripts: a program, a library, a script or a settings file that another account owns, or whose own permissions let another account change it, is kept with that owner and those permissions, which the hardening of the folders does not take away. Setup then runs programs from Bin with the administrator's elevated rights, and the service, which runs as LocalSystem or as its virtual account, runs them and the event script, so that a library such an account placed in Bin is loaded in place of the system's; the account can still change the file after the installation. The default installation under Program Files is not affected.