Authentication Bypass in MaxSite CMS via AJAX Dispatcher

Executive Summary

This vulnerability is an authentication bypass in MaxSite CMS 109.5 and earlier. It allows unauthenticated attackers to access admin-restricted endpoints by sending a specific X-Requested-With header and requesting a base64-encoded path that resolves to any *-ajax.php file. This bypasses authentication checks and enables attackers to interact with privileged plugin endpoints without credentials.

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Detection Guidance

Check for unauthorized access to admin-gated endpoints by monitoring requests to *-ajax.php files with base64-encoded paths and X-Requested-With headers. Inspect server logs for suspicious AJAX requests from unauthenticated sources.

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Impact Analysis

Attackers can exploit this flaw to manipulate admin-only functions such as poll states and vote counts. They can also reach other privileged plugin endpoints, potentially leading to unauthorized actions like data modification, system control, or further exploitation across the plugin ecosystem.

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Compliance Impact

This vulnerability allows unauthenticated attackers to access admin-restricted endpoints, potentially manipulating data like poll states or vote counts. For GDPR, this could lead to unauthorized access to personal data processing functions. For HIPAA, it may expose protected health information if admin-only AJAX endpoints handle such data. Non-compliance risks include data breaches and unauthorized modifications.

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Mitigation Strategies

Update MaxSite CMS to version 109.6 or later immediately. Disable automatic AJAX endpoint access until patched. Review server logs for signs of exploitation and restrict access to admin-only functions.

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