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Date: Tue, 22 Jan 2019 17:30:54 -0500
From: hyp3rlinx <>
Subject: [FD] Microsoft Windows .CONTACT File / HTML Injection Mailto:
	Remote Code Execution

[+] Credits: John Page (aka hyp3rlinx)
[+] Website:
[+] Source:
[+] ISR: ApparitionSec
[+] Zero Day Initiative Program
[+] ZDI-CAN-7591


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]
Mailto: HTML Link Injection Remote 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, the E-mail address
field takes an expected E-mail address value, however the .CONTACT file is
vulnerable to HTML injection as no validation is performed. Therefore, if
an attacker references an executable file using an HREF tag it will run that
instead without warning instead of performing the expected email behavior.
This is dangerous and would be unexpected to an end user.

The E-mail addresses Mailto: will point to an arbitrary executable like.
<a href="calc.exe"></a>

Additionally the executable file can live in a sub-directory and be
referenced like "<a href="mydir\malicious.exe"></a>" or
attackers can use
directory traversal techniques to point to a malware say sitting in the
targets Downloads directory like:

<a href="..\..\..\..\Users\victim\Downloads\evil.exe"></a>

Making matters worse is if the the files are compressed then downloaded
"mark of the web" (MOTW) may potentially not work as expected using certain
archive utils.

This advisory was initially one of three different vulnerabilities I
reported to Zero Day Initiative Program (ZDI), that microsoft decided to
not release a security fix
for and close. The first cases I reported to ZDI were .VCF and .CONTACT
files Website address input fields.

This example is yet another vector affecting Windows .CONTACT files and is
being released as the .CONTACT file issue is now publicly known.

Create a Windows .CONTACT file and inject the following HTML into the
E-mail: field

<a href="calc.exe"></a>

Windows will prompt you like "The e-mail address you have entered is not a
valid internet e-mail address. Do you still want to add this address?"

Click Yes.

Open the .CONTACT file and click the Mailto: link BOOM! Windows calculator
will execute.

Attacker supplied code is not limited to .EXE, .CPL or .COM as .VBS files
will also execute! :)

[POC Video URL]

[Disclosure Timeline]
Reported to ZDI 2018-11-22 (ZDI-CAN-7591)
Another separate vulnerability affecting MS Windows .contact files affected
the Website address input fields and was publicly disclosed January 16,
Public disclosure : January 22, 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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