Exponent CMS 2.6.0 patch2 - Stored XSS (User-Agent)

Description

Exponent CMS 2.6.0 patch2 allows an authenticated user to inject persistent javascript code on the User-Agent when logging in. When an administratoruser visits the 'User Sessions' tab, the javascript will be triggered allowingan attacker to compromise the administrator session.

PoC

1. Use a Web proxy or a tool to modify the browser User-agent with the following PoC.

   User-Agent: <script>alert('XSS')</script>

   User-Agent: <script>alert('XSS')</script>

   User-Agent: <script>alert('XSS')</script>

   User-Agent: <script>alert('XSS')</script>

2. Try to login with a non-admin user.

3. If an admin user visits 'User Management' > 'User Sessions' the XSS will be triggered.

A non-admin user may compromise an admin session by exploiting this vulnerability.

Our security policy

We have reserved the ID CVE-2022-23049 to refer to this issue from now on.

Disclosure policy

System Information

• Version: Exponent CMS 2.6.0 patch2.

• Operating System: Linux.

• Web Server: Apache

• PHP Version: 7.4

• Database and version: Mysql

References

• Vendor page: https://www.exponentcms.org/index.php

• GitHub repository: https://github.com/exponentcms/exponent-cms

• Ticket: https://exponentcms.lighthouseapp.com/projects/61783/tickets/1461

• Issue: https://github.com/exponentcms/exponent-cms/issues/1546

• Patch: https://github.com/exponentcms/exponent-cms/commit/4eec1a2d6def4a5369bda5fd63472dd706ea957a

Exploit

There is no exploit for the vulnerability but can be manually exploited.

Mitigation

An updated version of Exponent CMS is available on the vendor page.

Credits

The vulnerability was discovered by Oscar Uribe from Fluid Attacks' Offensive Team.