CVE-2023-53876
📋 TL;DR
Academy LMS 6.1 contains a file upload vulnerability that allows authenticated users to upload malicious SVG files containing stored cross-site scripting (XSS) payloads. Attackers can inject malicious JavaScript through the profile avatar upload feature by modifying file extensions, potentially compromising other users' sessions. This affects all Academy LMS 6.1 installations with authenticated user access.
💻 Affected Systems
- Academy LMS
📦 What is this software?
Academy Lms by Creativeitem
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, perform actions as other users, deface the application, or redirect users to malicious sites, potentially leading to full account compromise and data theft.
Likely Case
Authenticated attackers upload malicious SVG files that execute JavaScript in victims' browsers when viewed, allowing session hijacking, credential theft, or limited account takeover.
If Mitigated
With proper input validation and file type restrictions, the attack surface is reduced to authenticated users only, limiting impact to internal user compromise rather than external attacks.
🎯 Exploit Status
Exploit requires authenticated access; public exploit code is available on Exploit-DB (ID 51702).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://academylms.net/
Restart Required: No
Instructions:
Check Academy LMS vendor website for security updates or patches addressing CVE-2023-53876. Apply any available updates following vendor instructions.
🔧 Temporary Workarounds
Disable SVG file uploads
allConfigure the application to reject SVG file uploads through the profile avatar feature.
Modify application configuration to restrict allowed file types to non-SVG formats (e.g., PNG, JPG).
Implement server-side file validation
allAdd server-side checks to validate file content, not just extensions, and sanitize SVG files.
Implement file content validation in the upload handler to detect and block malicious SVG content.
🧯 If You Can't Patch
- Restrict user permissions to limit who can upload profile avatars.
- Implement web application firewall (WAF) rules to block malicious SVG uploads and XSS payloads.
🔍 How to Verify
Check if Vulnerable:
Attempt to upload an SVG file containing JavaScript payload through the profile avatar upload feature; if accepted and executes when viewed, the system is vulnerable.Check Version:
Check Academy LMS admin panel or configuration files for version information; typically found in application settings or about page.Verify Fix Applied:
Test that SVG files with embedded JavaScript are rejected or sanitized upon upload and do not execute in browsers.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with .svg extension
- Multiple failed upload attempts
- Log entries showing SVG file processing
Network Indicators:
- HTTP POST requests to avatar upload endpoints with SVG content
- Unexpected JavaScript execution in user sessions
SIEM Query:
source="web_server" AND (uri_path="/upload/avatar" OR file_extension=".svg") AND status=200