CVE-2026-28495: Php

Overview

A critical security vulnerability has been discovered in the massiveAdmin plugin bundled with GetSimple CMS. This flaw allows an attacker to take complete control of an affected website. Tracked as CVE-2026-28495, it has been rated with a critical CVSS score of 9.6, demanding immediate attention from administrators.

Vulnerability Details

The vulnerability exists in the massiveAdmin plugin version 6.0.3, which is included with GetSimpleCMS-CE version 3.3.22. The plugin’s configuration file editor lacks proper security controls. An authenticated administrator user can use this editor to overwrite the core gsconfig.php file with arbitrary PHP code. More critically, the form used for this action does not have Cross-Site Request Forgery (CSRF) protection.

This missing protection is the key to severe exploitation. A remote, unauthenticated attacker can craft a malicious web page. If a logged-in GetSimple CMS administrator visits this page, it can silently trigger a request from the administrator’s browser to the vulnerable CMS. This request can inject malicious PHP code into the configuration file, granting the attacker Remote Code Execution (RCE).

Impact

Successful exploitation grants an attacker full Remote Code Execution on the underlying web server. This means they can:

• Steal, modify, or delete all website data and files.
• Install backdoors for persistent access.
• Use the server to attack other internal systems.
• Deface the website or deploy malware.
• This can lead to a complete system compromise, significant data breaches, and severe reputational damage. For more on the consequences of such attacks, recent data breach reports are available at breach reports.

Remediation and Mitigation

Administrators must take action immediately to protect their systems.

Primary Action: Update or Remove The recommended course of action is to update GetSimple CMS and all plugins to the latest versions from the official source. If an immediate update is not possible, disable or completely remove the massiveAdmin plugin as a critical temporary measure. This will eliminate the attack vector.

Additional Security Measures:

1. Principle of Least Privilege: Review and minimize the number of administrator accounts. Ensure users only have the access levels absolutely necessary for their role.
2. User Vigilance: Administrators should be cautious about clicking links or visiting untrusted websites while logged into the CMS admin panel.
3. General Hygiene: Always maintain regular, offline backups of your website and database to enable recovery in case of an incident.

Stay informed about critical vulnerabilities like this by following the latest security news. For this specific issue, prioritize the removal of the vulnerable plugin or application of the official patch without delay.