CVE-2025-59543: Chamilo LMS Stored XSS Vulnerability

CVE-2025-59543 Overview

CVE-2025-59543 is a stored cross-site scripting (XSS) vulnerability in Chamilo, an open-source learning management system (LMS). Prior to version 1.11.34, the application fails to properly sanitize user input in the course description field, allowing attackers with low-privileged accounts (such as trainers) to inject malicious JavaScript code. When other users—including administrators—view the affected course information page, the injected script executes in their browser context.

Critical Impact

This vulnerability enables attackers to exfiltrate sensitive session cookies or authentication tokens, leading to account takeover (ATO) of higher-privileged users including administrators. Given that Chamilo is widely used in educational institutions, successful exploitation could compromise entire learning platforms and expose sensitive student and faculty data.

Affected Products

• Chamilo LMS versions prior to 1.11.34
• All Chamilo installations using vulnerable course description functionality
• Deployments where trainers or other low-privileged users can edit course information

Discovery Timeline

• 2026-03-06 - CVE-2025-59543 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2025-59543

Vulnerability Analysis

This stored XSS vulnerability (CWE-79) resides in the course description functionality of Chamilo LMS. The application accepts user-supplied HTML content in course description fields but fails to adequately sanitize or encode the input before rendering it to other users. This allows an attacker to persist malicious JavaScript payloads in the database, which then execute whenever any user views the compromised course page.

The attack is particularly dangerous because it targets a commonly accessed feature—course information pages—that administrators and other high-privileged users frequently visit. The stored nature of the vulnerability means the malicious payload persists until manually removed, potentially affecting numerous users over an extended period.

Root Cause

The root cause is improper input validation and output encoding in the course description handling mechanism. The application accepts rich HTML content to support legitimate formatting needs but does not implement sufficient XSS filters or Content Security Policy (CSP) controls to prevent script execution. User-supplied content is stored in the database and rendered directly to the browser without proper sanitization, creating a classic stored XSS condition.

Attack Vector

The attack follows a straightforward exploitation path:

1. An attacker authenticates with a low-privileged account (e.g., trainer role)
2. The attacker navigates to a course they can edit and accesses the course description field
3. Malicious JavaScript is injected into the description, such as script tags that steal session cookies or redirect authentication tokens to an attacker-controlled server
4. When administrators or other users view the course information page, the malicious script executes in their browser context
5. The attacker captures session tokens or cookies, enabling full account takeover

The network-based attack vector combined with the low privilege requirement and potential for scope change makes this vulnerability particularly severe. A single compromised trainer account can lead to administrative access across the entire Chamilo installation.

Detection Methods for CVE-2025-59543

Indicators of Compromise

• Unusual JavaScript code present in course description fields in the Chamilo database
• HTTP requests from internal users to unexpected external domains containing session tokens or credentials
• JavaScript event handlers (onload, onerror, onclick) embedded in course content
• Unexpected <script> tags or encoded script content in course descriptions

Detection Strategies

• Implement web application firewall (WAF) rules to detect XSS patterns in form submissions to course editing endpoints
• Monitor database tables storing course descriptions for suspicious script content or encoded JavaScript
• Review web server logs for unusual patterns of access to course pages followed by external requests
• Deploy browser-based Content Security Policy violation reporting to detect attempted script injection

Monitoring Recommendations

• Enable audit logging for all course description modifications in Chamilo
• Configure alerting for session token exposure or unusual cookie access patterns
• Monitor for privilege escalation events following course page views
• Implement anomaly detection for user sessions that suddenly access administrative functions

How to Mitigate CVE-2025-59543

Immediate Actions Required

• Upgrade Chamilo LMS to version 1.11.34 or later immediately
• Audit existing course descriptions for malicious JavaScript content
• Review access logs to identify potential exploitation attempts
• Force password resets for administrative accounts if compromise is suspected
• Implement Content Security Policy headers to restrict script execution sources

Patch Information

Chamilo has addressed this vulnerability in version 1.11.34. The patch implements proper input sanitization and output encoding for course description fields. Organizations should upgrade to this version or later to remediate the vulnerability. For detailed information about the security fix, refer to the GitHub Release v1.11.34 and the GitHub Security Advisory GHSA-p32q-6gh3-3gcv.

Workarounds

• Restrict course editing permissions to trusted users only until patching is complete
• Implement a web application firewall with XSS filtering rules for the Chamilo application
• Deploy Content Security Policy headers to prevent inline script execution
• Manually sanitize existing course descriptions by removing any script tags or event handlers

# Example: Apache Content Security Policy header configuration
# Add to .htaccess or httpd.conf for Chamilo installation
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"

# Example: Nginx CSP header configuration
# Add to server block for Chamilo
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';" always;