Advisory ID: SYSS-2018-007
Product: ILIAS
Affected Version(s): 5.3.2, 5.2.14, 5.1.25
Tested Version(s): 5.3.2, 5.2.12
Vulnerability Type: Reflected Cross-Site-Scripting
Risk Level: MEDIUM
Solution Status: Fixed
Manufacturer Notification: 2018-03-29
Solution Date: 2018-04-25
Public Disclosure: 2018-05-18
CVE Reference: CVE-2018-10428
Author of Advisory: Moritz Bechler, SySS GmbH

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Overview:

ILIAS is a e-Learning platform.

The manufacturer describes the product as follows (see [1]):

"ILIAS is a powerful Open Source Learning Management System for developing
 and realising web-based e-learning. The software was developed to reduce
 the costs of using new media in education and further training and to
 ensure the maximum level of customer influence in the implementation of
 the software. ILIAS is published under the General Public Licence and
 free of charge."

Due to inconsistencies in parameter handling ILIAS is vulnerable to
reflected cross-site-scripting in various locations.

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Vulnerability Details:

Request parameters handled through the saveParameter() mechanism can be
supplied through both URL parameters and application/x-www-form-urlencoded
POST bodies. These parameters will be included in the constructed HTML form
action URL without further encoding. While URL parameters are generally
sanitized by stripping HTML tags and a variety of characters, this is not
the case for parameters from the POST body.

Requesting a page with a saved parameter using a POST request, and supplying
that parameter inside the POST body, will therefor result in that value
being embedded into the page without proper escaping.

Instances of this issue have been identified in the ilStartupGui as well
as the ilCalendarAppointmentGUI pages, but there are likely more vulnerable
instances.

The necessary POST request can be initied by a third party site by
submitting a HTML form through JavaScript.
An attacker crafting such a site and tricking an user into visiting it
can therefor supply arbitrary JavaScript code to be executed in the
context of the target application.

This is suited to either execute arbitrary operations as an already
authenticated users or to steal a not-yet authenticated users credentials
by redirecting him to the regular login page with malicious JavaScript code
embedded sending them to a third-party server.

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Proof of Concept (PoC):


'seed' is a saved parameter for the add action of ilCalendarAppointmentGUI
which can be accessed via POST,

POST
/ILIAS-5.3.2/ilias.php?cmd=add&cmdClass=ilcalendarappointmentgui&cmdNode=zm:ao:b1&baseClass=ilPersonalDesktopGUI
HTTP/1.1
[...]
Cookie: PHPSESSID=[...]; ilClientId=test
Content-Type: application/x-www-form-urlencoded
[...]
seed="><script>alert(123)</script>


That request results in the <script> tag from the 'seed' value being
embedded in the response in multiple places so that a browser will
execute the JavaScript code.

HTTP/1.1 200 OK
[...]
<form id="form_" role="form"
class="form-horizontal preventDoubleSubmission"
action="ilias.php?seed="><script>alert(123)</script>
&cmd=post&cmdClass=ilcalendarappointmentgui&cmdNode=zm:ao:b1&baseClass=ilPersonalDesktopGUI&rtoken=[...]"
method="post" novalidate="novalidate">
[..]


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Solution:

Update to software version to ILIAS 5.3.4/5.2.15/5.1.26.

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Disclosure Timeline:

2018-03-26: Vulnerability discovered
2018-03-29: Vulnerability reported to manufacturer
2018-04-25: Patch released by manufacturer
2018-05-18: Public disclosure of vulnerability

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References:

[1] Product website for ILIAS
    https://github.com/ILIAS-eLearning/ILIAS
[2] SySS Security Advisory SYSS-2018-007
   
https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2018-007.txt
[3] SySS Responsible Disclosure Policy
    https://www.syss.de/en/news/responsible-disclosure-policy/

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Credits:

This security vulnerability was found by Moritz Bechler of SySS GmbH.

E-Mail: moritz.bechler@syss.de
Public Key: ://www.syss.de/fileadmin/dokumente/PGPKeys/Moritz_Bechler.asc
Key ID: 0x768EFE2BB3E53DDA
Key Fingerprint: 2C8F F101 9D77 BDE6 465E  CCC2 768E FE2B B3E5 3DDA

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Disclaimer:

The information provided in this security advisory is provided "as is"
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS Web
site.

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Copyright:

Creative Commons - Attribution (by) - Version 3.0
URL: https://creativecommons.org/licenses/by/3.0/deed.en