Stored XSS in AEM Design Importer Component

The impact of CVE-2020-9740 is significant due to the ease of exploitation and the potential for widespread impact. Attackers with 'Author' privileges, a relatively common role within AEM deployments, can leverage this vulnerability to inject malicious scripts. These scripts can then be stored within the AEM system and executed whenever a user views the affected page. This could allow an attacker to steal session cookies, redirect users to malicious websites, or even modify content on the AEM site. The stored nature of the XSS means that the malicious script persists until removed, allowing for repeated exploitation. Given AEM's role in many enterprise content management systems, a successful attack could compromise sensitive data and disrupt business operations.

Organizations heavily reliant on Adobe Experience Manager for content management, particularly those with large numbers of users with 'Author' privileges, are at significant risk. Environments with legacy AEM configurations or those lacking robust input validation practices are especially vulnerable. Shared hosting environments utilizing AEM also present a heightened risk due to the potential for cross-tenant exploitation.

• linux / server:

journalctl -u adobe-aem -g 'Design Importer' | grep -i 'script' 

• generic web:

curl -I <aem_url>/design-importer/ | grep -i 'content-type: javascript'

1. 2020-09-10Disclosure

   disclosure

2. 2020-09-10Patch

   patch

1. Reserviert2020-03-02
2. Veröffentlicht2020-09-10
3. Geändert2024-09-16
4. EPSS aktualisiert2026-04-02

The primary mitigation for CVE-2020-9740 is to upgrade to Adobe Experience Manager version 6.5.6 or later, which contains the fix. If an immediate upgrade is not possible, consider implementing temporary workarounds. Restrict access to the Design Importer feature to only authorized personnel. Implement strict input validation and sanitization on all user-supplied data within the Design Importer. Web Application Firewalls (WAFs) configured to detect and block XSS payloads can provide an additional layer of defense. Monitor AEM logs for suspicious activity, particularly related to the Design Importer feature. After upgrading, confirm the vulnerability is resolved by attempting to inject a test script through the Design Importer and verifying that it is not executed.