CVE-2025-64840 is a stored Cross-Site Scripting (XSS) vulnerability identified in Adobe Experience Manager (AEM) versions 6.5.23 and earlier. Stored XSS occurs when malicious input is saved by the application and later rendered in users' browsers without proper sanitization or encoding. In this case, a low-privileged attacker can exploit vulnerable form fields within AEM to inject arbitrary JavaScript code. When other users access pages containing the injected script, it executes in their browsers, potentially allowing attackers to steal session cookies, perform actions on behalf of the user, or redirect users to malicious sites. The vulnerability requires the attacker to have at least low privileges to submit malicious input and requires user interaction (victims must visit the compromised page). The CVSS 3.1 score of 5.4 reflects network attack vector (remote), low attack complexity, low privileges required, but user interaction needed, and a scope change indicating that the vulnerability affects components beyond the initially vulnerable system. The impact affects confidentiality and integrity but not availability. No public exploits or patches are currently available, but Adobe has published the vulnerability details, indicating a patch is likely forthcoming. The vulnerability is classified under CWE-79, a common and well-understood web security issue. Given AEM's role as a widely used enterprise web content management system, exploitation could affect many organizations that rely on it for public-facing websites and internal portals.

For European organizations, this vulnerability poses a moderate risk primarily to confidentiality and integrity of user sessions and data. Attackers exploiting this flaw could hijack user sessions, steal sensitive information such as authentication tokens or personal data, and perform unauthorized actions within the context of the victim’s privileges. This can lead to reputational damage, regulatory non-compliance (e.g., GDPR breaches), and potential financial losses. Since AEM is often used by large enterprises, government agencies, and public institutions in Europe, the impact could extend to critical infrastructure and services. The vulnerability does not affect availability, so denial-of-service is not a concern here. However, the ability to execute arbitrary scripts in users’ browsers can facilitate phishing, malware distribution, and lateral movement within networks. The medium CVSS score reflects these considerations, but the real-world impact depends on the deployment context and the sensitivity of the data handled by the affected AEM instances.

1. Apply official Adobe patches immediately once released for AEM versions 6.5.23 and earlier. 2. Until patches are available, implement strict input validation and sanitization on all form fields to block malicious script tags and event handlers. 3. Employ robust output encoding (e.g., HTML entity encoding) when rendering user-supplied data in web pages to prevent script execution. 4. Configure Content Security Policy (CSP) headers to restrict the sources of executable scripts and reduce the impact of injected scripts. 5. Conduct regular security audits and penetration testing focused on web application inputs and outputs. 6. Educate users and administrators about the risks of XSS and encourage cautious behavior when interacting with web forms. 7. Monitor web server logs and application behavior for unusual input patterns or error messages indicative of exploitation attempts. 8. Consider deploying web application firewalls (WAFs) with rules targeting XSS payloads as an additional protective layer. 9. Limit user privileges to the minimum necessary to reduce the risk posed by low-privileged attackers. 10. Maintain an incident response plan to quickly address potential exploitation events.