Reflected XSS in Cotonti message.php via lng Parameter

Executive Summary

CVE-2026-100522 is a reflected cross-site scripting (XSS) vulnerability in Cotonti versions up to 1.0.0. The issue occurs in message.php where the lng parameter is not properly escaped before being reflected in a confirmation dialog. Attackers can exploit this by crafting malicious URLs with script payloads in the lng parameter to execute arbitrary JavaScript in victims' browsers.

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Detection Guidance

To detect this reflected XSS vulnerability, monitor network traffic for requests to message.php with the lng parameter containing script tags or unusual payloads. Check server logs for suspicious URLs like 'message.php?lng=<script>alert(1)</script>'. Use tools like Burp Suite or OWASP ZAP to intercept and inspect requests for the lng parameter.

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Impact Analysis

This vulnerability allows unauthenticated attackers to execute arbitrary JavaScript in your browser session when you visit a crafted link. This could lead to session hijacking, theft of cookies or sensitive data, defacement of web pages, or redirection to malicious sites. Users of vulnerable Cotonti installations are at risk if they interact with untrusted links.

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Compliance Impact

This XSS vulnerability could lead to unauthorized access to user data, which may violate GDPR's data protection requirements or HIPAA's security rules for protected health information. Organizations using vulnerable Cotonti versions may face compliance violations if user data is compromised through this flaw.

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Mitigation Strategies

Immediately update Cotonti to the latest patched version. If patches are not available, apply input validation to sanitize the lng parameter in message.php. Consider implementing a web application firewall (WAF) to block malicious payloads in the lng parameter. Review and restrict user-supplied input handling in all parameters.

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