CVE-2020-9732 in Experience Manager
Summary
by MITRE
The AEM Forms add-on for versions 6.5.5.0 (and below) and 6.4.8.2 (and below) are affected by a stored XSS vulnerability that allows users with 'Author' privileges to store malicious scripts in fields associated with the Sites component. These scripts may be executed in a victim’s browser when they open the page containing the vulnerable field.
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Analysis
by VulDB Data Team • 11/13/2020
The vulnerability identified as CVE-2020-9732 represents a critical stored cross-site scripting flaw within Adobe Experience Manager Forms add-on versions 6.5.5.0 and earlier, as well as 6.4.8.2 and earlier releases. This vulnerability specifically targets the Sites component functionality where users with 'Author' privileges can inject malicious scripts into fields that are subsequently stored within the system. The flaw exists in the input validation and output encoding mechanisms of the AEM Forms add-on, creating an environment where persistent malicious code can be embedded and later executed in the browsers of unsuspecting users who access pages containing these compromised fields. The vulnerability stems from inadequate sanitization of user input data before storage, allowing attackers to craft malicious payloads that persist within the application's database or content repository.
The technical exploitation of this vulnerability follows a specific attack pattern where an attacker with 'Author' privileges leverages their access rights to modify content fields within the Sites component. When malicious scripts are stored in these fields, they become part of the normal content delivery process and execute automatically when victims browse to pages containing the compromised content. The vulnerability is classified as a stored XSS (CWE-79) as the malicious payload is stored server-side and executed during subsequent page requests rather than being reflected in the HTTP response. This makes the attack more persistent and potentially more damaging than reflected XSS attacks, as the malicious code can affect multiple users over extended periods. The attack vector involves the attacker creating a crafted script that, when rendered in a victim's browser, can perform actions such as stealing session cookies, redirecting users to malicious sites, or executing unauthorized operations within the application context.
The operational impact of CVE-2020-9732 extends beyond simple script execution as it provides attackers with a foothold for more sophisticated attacks within the AEM environment. Successful exploitation can lead to unauthorized access to user sessions, data exfiltration, and potential lateral movement within the application infrastructure. The vulnerability affects organizations using AEM Forms in production environments where content authors have elevated privileges, creating a significant risk for companies that rely on AEM for digital experience management. Attackers can leverage this vulnerability to harvest sensitive information from authenticated users, potentially compromising the entire content management system. The persistence of stored XSS payloads means that the vulnerability remains active until the malicious content is removed from the system, making it particularly dangerous in environments where content is frequently updated or where content authors have broad editing capabilities. This vulnerability also violates several security principles outlined in the ATT&CK framework, specifically targeting the 'Initial Access' and 'Persistence' phases of the attack lifecycle.
Organizations affected by CVE-2020-9732 should immediately implement comprehensive mitigations including upgrading to patched versions of AEM Forms, implementing strict input validation and output encoding mechanisms, and conducting thorough security reviews of all content fields that accept user input. The recommended approach includes enabling Content Security Policy headers, implementing proper sanitization of all user inputs, and restricting 'Author' privileges to only those users who require such access for legitimate business purposes. Security teams should also deploy monitoring solutions to detect anomalous content modifications and establish incident response procedures for identifying and removing malicious payloads. Additionally, organizations should consider implementing web application firewalls to provide an additional layer of protection against XSS attacks and ensure that all users with content authoring privileges undergo proper security training to prevent accidental or intentional exploitation of such vulnerabilities. The mitigation strategy should align with industry best practices for preventing XSS attacks as outlined in OWASP Top 10 and NIST cybersecurity frameworks.