CVE-2020-9742 in Experience Manager
Summary
by MITRE
AEM versions 6.5.5.0 (and below), 6.4.8.1 (and below) and 6.3.3.8 (and below) are affected by a stored XSS vulnerability that allows users with 'Author' privileges to store malicious scripts in fields associated with the Inbox calendar feature. 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 described in CVE-2020-9742 represents a critical stored cross-site scripting flaw within Adobe Experience Manager platforms. This security weakness affects multiple versions of AEM including 6.5.5.0 and earlier, 6.4.8.1 and earlier, and 6.3.3.8 and earlier releases. The vulnerability specifically targets the Inbox calendar feature, which is a core component of AEM's content management capabilities that allows users to manage and schedule content activities. The flaw enables attackers with 'Author' privileges to inject malicious scripts into calendar-related fields, creating a persistent threat that can compromise user sessions and execute unauthorized actions against the application.
The technical nature of this vulnerability stems from insufficient input validation and output encoding within the calendar feature's data handling mechanisms. When authors input data into calendar fields, the system fails to properly sanitize or escape special characters that could be interpreted as executable script code. This allows malicious actors to store JavaScript payloads within calendar entries that will be rendered when other users view these entries. The vulnerability operates under CWE-79 which categorizes cross-site scripting flaws as weaknesses in input validation and output encoding. The attack vector specifically aligns with ATT&CK technique T1566.001 which involves the use of malicious content to compromise systems through web-based attacks.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities. When victims view calendar entries containing the stored scripts, the malicious code executes in their browser context, potentially allowing attackers to steal session cookies, redirect users to phishing sites, or perform unauthorized actions within the AEM environment. The privilege escalation aspect is particularly concerning since attackers need only 'Author' level access, which is relatively common among content creators and editors in typical AEM deployments. This makes the vulnerability exploitable in environments where multiple users have varying levels of access, increasing the potential attack surface significantly.
Organizations affected by this vulnerability should prioritize immediate remediation through official Adobe patches and updates. The recommended mitigation strategy involves applying the latest security patches released by Adobe for the affected AEM versions, which typically include enhanced input validation and proper output encoding mechanisms. Additionally, implementing network-level protections such as web application firewalls and content security policies can provide additional defense-in-depth measures. Security teams should also consider implementing monitoring solutions to detect unusual calendar data modifications and conduct regular security assessments to identify potential exploitation attempts. The vulnerability demonstrates the critical importance of validating user inputs and properly encoding output data, particularly in content management systems where users have the ability to modify application features and data fields.