Hi @ll,

Malwarebytes executable installers mbam-setup-2.2.0.1024.exe
and mbae-setup-1.08.1.1189.exe (available from
<https://downloads.malwarebytes.org/file/mbam_current/> and
<https://downloads.malwarebytes.org/file/mbae_current/>) load
and execute UXTheme.dll and DWMAPI.dll from their "application
directory".

For software downloaded with a web browser the application
directory is typically the user's "Downloads" directory: see
<https://insights.sei.cmu.edu/cert/2008/09/carpet-bombing-and-directory-poisoning.html>,
<http://blog.acrossecurity.com/2012/02/downloads-folder-binary-planting.html>
and <http://seclists.org/fulldisclosure/2012/Aug/134>


If an attacker places UXTheme.dll and/or DWMAPI.dll in the user's
"Downloads" directory, for example per "drive-by download" or
"social engineering", this vulnerability becomes a remote code
execution.

Due to the application manifest embedded in the executables which
specifies "requireAdministrator" the executable installers are run
with administrative privileges ("protected" administrators are
prompted for consent, unprivileged standard users are prompted for
an administrator password); execution of the DLLs therefore results
in an escalation of privilege!


Proof of concept/demonstration:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. visit <http://home.arcor.de/skanthak/sentinel.html>, download
   <http://home.arcor.de/skanthak/download/SENTINEL.DLL>, save it
   as UXTheme.dll in your "Downloads" directory, then copy it as
   DWMAPI.dll;

2. download mbam-setup-2.2.0.1024.exe and mbae-setup-1.08.1.1189.exe
   and save them in your "Downloads" directory;

3. execute mbam-setup-2.2.0.1024.exe and mbae-setup-1.08.1.1189.exe
   from your "Downloads" directory;

4. notice the message boxes displayed from the DLLs placed in step 1.

PWNED!


See <http://seclists.org/fulldisclosure/2015/Nov/101>,
<http://seclists.org/fulldisclosure/2015/Dec/86> and
http://seclists.org/fulldisclosure/2015/Dec/33 plus
<http://home.arcor.de/skanthak/!execute.html> and
<http://home.arcor.de/skanthak/sentinel.html> for details about
this well-known and well-documented BEGINNER'S error!


regards
Stefan Kanthak


PS: I really LOVE (security) software with such trivial beginner's
    errors. It's a tell-tale sign to stay away from this snakeoil!


Timeline:
~~~~~~~~~

2015-12-25    sent report regarding MBAM to vendor

2015-12-25    automatic reply from vendor:
              "We have received your request and an agent will respond
               to your ticket in the order in which it was received."

2016-01-03    reply from vendor:
              "We'll take this into consideration for a near-future
               installer revamp."

2016-02-02    requested status update

              NO REPLY, not even an acknowledgement of receipt

2016-02-02    sent notice to Marcin Kleczynski after his public
              announcement of a bug bounty program

2016-02-02    reply from Marcin Kleczynski:
              "I'm copying Pedro Bustamante who organizes our bug
               bounty program to take a look."

              NO reply from Pedro Bustamante et.al.

2016-02-12    sent report regarding MBAE to vendor

              NO REPLY, not even an acknowledgement of receipt

2016-02-22    resent report regarding MBAE to vendor

              NO REPLY, not even an acknowledgement of receipt

2016-03-06    report published in accordance with my disclosure
              policy <http://home.arcor.de/skanthak/policy.html>