Stored XSS in AEM Forms component

The impact of CVE-2020-9734 is significant due to the potential for remote code execution within a user's browser. An attacker could leverage this vulnerability to steal sensitive information, such as session cookies, allowing them to impersonate legitimate users. They could also inject malicious content into the Forms page, redirecting users to phishing sites or delivering malware. Given the 'Author' privilege requirement, the attack would likely target users with elevated permissions within the AEM Forms environment, potentially granting access to broader systems and data. The stored nature of the XSS means the malicious script persists until removed, allowing for repeated exploitation.

Organizations heavily reliant on Adobe AEM Forms for critical business processes are at significant risk. Specifically, deployments with a large number of users with 'Author' privileges, or those lacking robust input validation and sanitization practices, are particularly vulnerable. Shared hosting environments where multiple tenants share the same AEM Forms instance are also at increased risk, as a compromise of one tenant could potentially affect others.

• java / server: Monitor AEM Forms logs for unusual script injections or unexpected user behavior. Look for patterns indicative of XSS payloads in form field data.

grep -i 'script|onload|onerror' /path/to/aem/logs/error.log

• generic web: Use curl to test form submissions with potentially malicious input. Examine the resulting HTML for evidence of script execution.

curl -X POST -d "<script>alert('XSS')</script>" http://aem-server/forms/submit.html

• generic web: Check response headers for unusual content-security-policy (CSP) configurations that might be bypassed.

curl -I http://aem-server/forms/submit.html | grep Content-Security-Policy

1. 2020-09-10Disclosure

   disclosure

1. Gereserveerd2020-03-02
2. Gepubliceerd2020-09-10
3. Gewijzigd2024-09-17
4. EPSS bijgewerkt2026-04-02

As Adobe has not released a fixed version for CVE-2020-9734, mitigation strategies focus on reducing the attack surface and detecting malicious activity. Implement strict input validation and sanitization on all user-supplied data within AEM Forms. Consider restricting 'Author' privileges to only those users who absolutely require them. Employ a Web Application Firewall (WAF) with XSS protection rules to filter out potentially malicious requests. Regularly monitor AEM Forms logs for suspicious activity, such as unusual script injections or unexpected user behavior. While not a direct fix, these measures can significantly reduce the risk of exploitation.