CVE-2026-39878 in Chamilo
Summary
by MITRE • 07/20/2026
Chamilo LMS versions 1.11.38 and earlier contain a stored cross-site scripting vulnerability in the user registration form that allows any unauthenticated attacker to execute arbitrary JavaScript in an administrator's browser session, leading to full platform admin account takeover. This has been patched in 1.11.40.
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Analysis
by VulDB Data Team • 07/20/2026
The Chamilo Learning Management System presents a critical stored cross-site scripting vulnerability affecting versions 1.11.38 and earlier, which represents a significant security flaw in the platform's user registration mechanism. This vulnerability stems from inadequate input validation and sanitization within the registration form processing logic, where user-supplied data is not properly escaped or filtered before being stored and subsequently rendered in administrative interfaces. The flaw allows unauthenticated attackers to inject malicious javascript code through the registration form fields, which then gets executed when administrators view the user records, creating a persistent threat vector that can be exploited without requiring prior authentication credentials.
The technical exploitation of this vulnerability follows a specific attack pattern where an attacker registers with a malicious payload in one of the user input fields such as username, email, or profile information. When the administrator accesses the user management section to review or edit the registered user data, the stored javascript code executes within the administrator's browser session context. This execution context is particularly dangerous because it operates with the privileges and permissions of the authenticated administrator, enabling attackers to perform actions such as modifying user roles, accessing sensitive course materials, changing system configurations, or even creating new administrative accounts. The vulnerability specifically targets the server-side processing of user registration data that lacks proper output encoding for cross-site scripting protection.
The operational impact of this vulnerability extends beyond simple session hijacking, as it provides attackers with complete control over the Chamilo platform administration interface. Successful exploitation can result in unauthorized access to student records, course content manipulation, system configuration changes, and potential data exfiltration from the learning management environment. The stored nature of the vulnerability means that once an attacker successfully injects malicious code, it remains persistent and will continue to execute whenever administrators view the affected user records, creating a long-term threat vector that can persist even after initial exploitation attempts. This vulnerability particularly affects educational institutions relying on Chamilo LMS for their online learning platforms, potentially compromising sensitive academic data and institutional security.
The remediation for this vulnerability requires immediate patching of the affected Chamilo LMS versions to 1.11.40 or later, which includes proper input sanitization and output encoding mechanisms in the user registration form processing. Security teams should implement comprehensive input validation that filters or escapes special characters in all user-supplied data before storage, while also ensuring that stored data is properly encoded when rendered in administrative interfaces. Organizations should conduct thorough security assessments of their Chamilo installations to identify any potential exploitation attempts and monitor system logs for suspicious registration activities. Additionally, implementing web application firewalls with XSS detection capabilities and regular security audits can provide additional defense layers against similar vulnerabilities in the platform's architecture.
This vulnerability aligns with CWE-79 which identifies cross-site scripting as a fundamental weakness in web application security, specifically addressing the improper neutralization of input during web page generation. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1078 which covers valid accounts and privilege escalation through administrative access compromise. The attack chain typically follows initial reconnaissance to identify vulnerable systems, followed by registration with malicious payloads, and culminates in administrator session takeover and persistent access to the platform's administrative functions. Security practitioners should consider this vulnerability as part of broader web application security controls that include proper input validation, output encoding, and regular software update management practices to prevent similar threats from compromising educational technology platforms.