Document Title:
===============
GhostMail - (filename to link) POST Inject Web Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=1471


Release Date:
=============
2018-06-26


Vulnerability Laboratory ID (VL-ID):
====================================
1471


Common Vulnerability Scoring System:
====================================
4.2


Vulnerability Class:
====================
Cross Site Scripting - Persistent


Current Estimated Price:
========================
500a! - 1.000a!


Product & Service Introduction:
===============================
Sign up to military grade encrypted GhostMail and enjoy instant free and
secure email & chat. No download or installs needed.
GhostMail is your new secure email & chat platform, with great features
like self destruction, two factor login and much more...
Join free today and start enforcing your privacy and online rights.

(Copy of the Vendor Homepage: https://www.ghostmail.com/ )


Abstract Advisory Information:
==============================
The vulnerability laboratory core research team discovered an
application-side vulnerability in the official GhostMail chat online
service web-application.


Vulnerability Disclosure Timeline:
==================================
2018-06-26: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
GhostCom Ltd.
Product: GhostMail (Chat) - Web Application (Online Service) 2015 Q2


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


Authentication Type:
====================
Restricted authentication (user/moderator) - User privileges


User Interaction:
=================
Low User Interaction


Disclosure Type:
================
Bug Bounty Program


Technical Details & Description:
================================
An application-side input validation web vulnerability has been
discovered in the official Ghostmail online service web-application.
The vulnerability allows remote attackers to inject own script codes on
the application-side of the affected web-application module.

The vulnerability is located in the `file attach link` and `filename`
value of the `ghostmail - mail` module. The filename and
file attach link input values are wrong encoded. The vulnerability
allows remote attackers to inject own script code to the
application-side of the vulnerable module. The request method to inject
the script code is POST and the attack vector is persistent.

The security risk of the persistent web vulnerability is estimated as
medium with a cvss (common vulnerability scoring system) count of 3.7.
Exploitation of the persistent input validation vulnerability requires a
low privileged web-application user account and low user interaction.
Successful exploitation results in session hijacking, persistent
phishing attacks, persistent external redirect and malware loads or
persistent
manipulation of affected and connected module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] Ghostmail/mail

Vulnerable Input(s):
[+] File attach link

Vulnerable Parameter(s):
[+] filename


Proof of Concept (PoC):
=======================
The application-side web vulnerability can be exploited by remote
attackers with low privileged application user account and low user
interaction.
For security demonstration or to reproduce the security vulnerability
follow the provided information and steps below to continue.


PoC: Payload (Exploitation)
<a
href="blob:https://www.ghostmail.com/13cfcc29-03fb-4d94-9ad8-c372ddaa02fd"
download="" filename="../"[MALICIOUS SCRIPT CODE PAYLOAD!]">"></a>


Manual steps to reproduce the security vulnerability ...
1. Opne the ghostmail online service page and login
2. Move to the ./mail path of the application
3. Start a session tamper for http protocols to intercept
4. Inject your own script code in the name of attach file parameter
during the request
Note: There's a script code injection vulnerability in the link for the
file attach (attachment) parameter
Note: In the link to download the file and in the download="name file"
use "title="THIS IS A VULN_LAB TEST"
5. When you will upload a file with name "filename="
6. The link in the attachment changes and cannot download the file
because the link has no name specification for downloading
Note: <a
href="blob:https://www.ghostmail.com/13cfcc29-03fb-4d94-9ad8-c372ddaa02fd"
download="" filename="[MALICIOUS SCRIPT CODE PAYLOAD!]>"></a>
7. Successful reproduce of the vulnerability!


Reference(s):
https://www.ghostmail.com/
https://www.ghostmail.com/13cfcc29-03fb-4d94-9ad8-c372ddaa02fd


Solution - Fix & Patch:
=======================
The vulnerability can be patched by a parse and encode of the vulnerable
filename and link to filename value in the upload POST method request.
Restrict the input and disallow special chars. Escape the web context to
prevent an application-side script code execution vulnerability.

The vulnerability has been reported 2016-10-01. The issue was resolved
during the 2017 Q2 - Q4 by the ghost mail developer team.


Security Risk:
==============
The security risk of the application-side input validation web
vulnerability in the ghostmail mail module is estimated as medium (CVSS
4.2).


Credits & Authors:
==================
Vulnerability-Lab [research@vulnerability-lab.com] -
https://www.vulnerability-lab.com/show.php?user=Vulnerability-Lab


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=========================
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