Hi @ll

despite better knowledge and MULTIPLE bug/vulnerability reports
(see <https://bugzilla.mozilla.org/show_bug.cgi?id=811557>,
<https://bugzilla.mozilla.org/show_bug.cgi?id=809373>, 
<https://bugzilla.mozilla.org/show_bug.cgi?id=579593>, ...)
Mozilla continues to ship Firefox and Thunderbird for Windows with
a vulnerable executable installer.


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

1. visit <https://home.arcor.de/skanthak/sentinel.html>, download
   <https://home.arcor.de/skanthak/download/SENTINEL.DLL> and save
   it as ShimEng.dll in your "Downloads" folder, then copy it as
   WinMM.dll, SetupAPI.dll, MSACM32.dll, UXTheme.dll, DWMAPI.dll,
   ShFolder.dll, RichEd20.dll, ClbCatQ.dll, COMRes.dll, Version.dll,
   SAMCli.dll, SFC.dll, SFC_OS.dll, UserEnv.dll, ProfAPI.dll, MPR.dll,
   NTMarta.dll, Secur32.dll and CryptSP.dll

2. download any full-package installer for Firefox or Thunderbird
   from <https://ftp.mozilla.org/pub/firefox/releases/.../win32/...>
   or <https://ftp.mozilla.org/pub/thunderbird/releases/.../win32/...>
   (these are self-extractors built with 7-zip)

3. extract setup.exe from the downloaded self-extractor and save it
   in your "Downloads" folder, for example using the command line
      7za.exe x <self-extractor> setup.exe

   (or start the downloaded self-extractor, find the temporary
   subdirectory 7z*.tmp it created below %TEMP% and copy setup.exe
   from this subdirectory to your "Downloads" folder)

4. execute the extracted/copied setup.exe and notice the message
   boxes displayed from the DLL(s) downloaded in step 1:

PWNED!


See <https://cwe.mitre.org/data/definitions/426.html>,
<https://cwe.mitre.org/data/definitions/427.html> plus
<https://capec.mitre.org/data/definitions/471.html> for the
well-known and well-documented DLL search path vulnerability.


Mitigation:
~~~~~~~~~~~
Stay away from Mozilla's crapware until Mozilla starts to develop
a sense for the basics of software engineering as well as the safety
and security of their users^Wvictims: the authors of the 3rd party
installer fixed these vulnerabilities about 4 months ago!


JFTR: the vulnerable executable installer is not the only outdated
      3rd party component used to build Firefox and Thunderbird!
      Mozilla even uses different versions of this vulnerable
      executable installer for Firefox and Firefox ESR.


See <https://www.firegiant.com/blog/2016/1/20/wix-v3.10.2-released/>
why you should NEVER name any executable (installer) setup.exe!


stay tuned
Stefan Kanthak


PS: Mozilla fixed the same vulnerabilities in their executable self-
    extractor long ago (see for example
    <https://bugzilla.mozilla.org/show_bug.cgi?id=792106> or
    <https://bugzilla.mozilla.org/show_bug.cgi?id=883165>), but
    apparently did not send their fixes to the author of this tool.