CVE-2020-9734
📋 TL;DR
This stored XSS vulnerability in Adobe Experience Manager Forms allows authenticated users with 'Author' privileges to inject malicious scripts into form fields. When other users view pages containing these compromised forms, the scripts execute in their browsers, potentially leading to session hijacking or data theft. The vulnerability affects AEM Forms add-on versions 6.5.5.0 and below, and 6.4.8.1 and below.
💻 Affected Systems
- Adobe Experience Manager Forms add-on
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers with author privileges could steal administrator credentials, compromise user sessions, deface websites, or redirect users to malicious sites, potentially leading to full system compromise.
Likely Case
Attackers with author access could steal session cookies, perform actions as authenticated users, or capture sensitive form data submitted by victims.
If Mitigated
With proper input validation and output encoding, the risk is reduced to minimal, though the vulnerability still exists in the codebase.
🎯 Exploit Status
Exploitation requires authenticated access with 'Author' privileges. The vulnerability is straightforward to exploit once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply AEM Forms Service Pack 6.5.6.0 or 6.4.8.2
Vendor Advisory: https://helpx.adobe.com/security/products/experience-manager/apsb20-56.html
Restart Required: Yes
Instructions:
1. Download the appropriate service pack from Adobe's distribution portal. 2. Backup your AEM instance. 3. Stop the AEM service. 4. Apply the service pack according to Adobe's installation instructions. 5. Restart the AEM service. 6. Verify the update was successful.
🔧 Temporary Workarounds
Input Validation Filter
allImplement server-side input validation to sanitize all user input in Forms component fields
Implement custom servlet filter or use AEM's built-in XSS protection features
Output Encoding
allApply proper output encoding when rendering form field data to prevent script execution
Use HTL/HTL-Sightly output encoding or implement custom encoding in JSPs
🧯 If You Can't Patch
- Restrict 'Author' role privileges to trusted users only and implement strict access controls
- Implement Content Security Policy (CSP) headers to restrict script execution from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check AEM Forms version via AEM Web Console (/system/console/bundles) or by examining installed packagesCheck Version:
Check CRX Package Manager or AEM Web Console for installed AEM Forms versionVerify Fix Applied:
Verify version is updated to 6.5.6.0 or higher, or 6.4.8.2 or higher, and test form fields for XSS payload acceptance📡 Detection & Monitoring
Log Indicators:
- Unusual form submissions with script tags or JavaScript payloads
- Multiple failed login attempts followed by successful author access
Network Indicators:
- Unexpected outbound connections from AEM server after form submissions
- Suspicious JavaScript payloads in HTTP requests
SIEM Query:
source="aem_logs" AND ("script" OR "javascript" OR "onload" OR "onerror") AND "form_submission"