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Date: Wed, 16 Jan 2019 22:08:39 -0500
From: hyp3rlinx <>
Subject: [FD] Microsoft Windows ".contact" File / Insufficient UI Warning
 Arbitrary Code Execution

[+] Credits: John Page (aka hyp3rlinx)
[+] Website:
[+] Source:
[+] ISR: ApparitionSec


Microsoft .CONTACT File

A file with the CONTACT file extension is a Windows Contact file. They're
used in Windows 10, Windows 8, Windows 7, and Windows Vista.
This is the folder where CONTACT files are stored by default:

[Vulnerability Type]
Insufficient UI Warning Arbitrary Code Execution

[Security Issue]
This vulnerability allows remote attackers to execute arbitrary code on
vulnerable installations of Microsoft Windows.
User interaction is required to exploit this vulnerability in that the
target must visit a malicious page or open a malicious file.

The flaw is due to the processing of ".contact" files <c:Url> node param
which takes an expected website value, however if an attacker references an
executable file it will run that instead without warning instead of
performing expected web navigation. This is dangerous and would be
unexpected to an end user.


<c:Url c:ElementID="xxxxxxxxxxxxxxxxxxxxxxxx"><c:Value></c:Value>

Executable files can live in a sub-directory so when the ".contact" website
link is clicked it traverses directories towards the executable and runs.
Making matters worse is if the the files are compressed then downloaded
"mark of the web" (MOTW) may potentially not work as expected with certain
archive utilitys.

The ".\" chars allow directory traversal to occur in order to run the
attackers supplied executable sitting unseen in the attackers directory.
This advisory is a duplicate issue that currently affects Windows .VCF
files, and released for the sake of completeness as it affects Windows
.contact files as well.

Rename any executable file extension from ".exe" to ".com" to be like a
valid web domain name.
Create a directory to house the executable file
Modify the contact file website link like --->
Contact website link now points at "dir .\ executable"  --->
Compress the files using archive utility and place in webserver for

[POC Video URL]

[Disclosure Timeline]
Reported to ZDI 2018-11-30
This exact same vulnerability exists and affects Microsoft Windows .VCF
files sharing the same root cause and was publicly disclosed 2019-01-10.
Public disclosure : January 16, 2019

[+] Disclaimer
The information contained within this advisory is supplied "as-is" with no
warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and
that due credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit
is given to the author. The author is not responsible for any misuse of the
information contained herein and accepts no responsibility
for any damage caused by the use or misuse of this information. The author
prohibits any malicious use of security related information
or exploits by the author or elsewhere. All content (c).


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