Reflected XSS in AEM Inbox module

The impact of CVE-2020-9742 is significant due to the potential for widespread compromise within an AEM environment. An attacker who gains 'Author' privileges can leverage this XSS vulnerability to execute arbitrary JavaScript code in the browsers of other users, including administrators. This could allow them to steal session cookies, redirect users to malicious websites, deface the AEM interface, or even gain control of the entire AEM instance. The stored nature of the vulnerability means that the malicious script persists until removed, allowing for repeated exploitation. This is particularly concerning in environments where the Inbox calendar feature is heavily used for internal communications and scheduling, as it provides a broad attack surface.

Organizations heavily reliant on Adobe Experience Manager for content management and digital asset management are at significant risk. Specifically, deployments utilizing the Inbox module and granting 'Author' privileges to a large number of users are particularly vulnerable. Shared hosting environments where multiple AEM instances share resources could also be affected, potentially allowing an attacker to compromise multiple instances through a single vulnerability.

• other / web:

curl -I 'https://<aem_server>/inbox/calendar?field=<malicious_script>' | grep -i 'content-type: text/html'

• other / web:

 grep -i '<script>alert("XSS")</script>' /var/log/apache2/access.log

• other / web:

 grep -i '<script>alert("XSS")</script>' /var/log/apache2/error.log

1. 2020-09-10Disclosure

   disclosure

2. 2020-09-10Discovery

   published

1. Reserviert2020-03-02
2. Veröffentlicht2020-09-10
3. Geändert2024-09-17
4. EPSS aktualisiert2026-04-02

Given that Adobe has not yet released a fixed version for CVE-2020-9742, immediate mitigation strategies are crucial. The primary recommendation is to restrict access to the Inbox calendar feature to only authorized personnel. Implement strict input validation and sanitization on all fields associated with the calendar to prevent the injection of malicious scripts. Consider using a Web Application Firewall (WAF) with XSS protection rules to filter out potentially malicious requests. Regularly scan the AEM environment for suspicious scripts and user activity. While a direct patch is unavailable, carefully review Adobe's security advisories for any interim guidance or workarounds. After implementing these controls, verify their effectiveness by attempting to inject a benign test script into a calendar field and confirming that it is properly sanitized.