CVE-2025-65203 is a vulnerability affecting KeePassXC-Browser up to version 1.9.9.2, where the browser extension autofills or prompts users to fill stored credentials into web documents rendered inside iframes that are sandboxed and governed by browser-enforced Content Security Policy (CSP) directives. Normally, sandbox attributes and CSPs restrict script execution and data access within these iframes, isolating potentially untrusted content. However, due to improper handling of autofill behavior, attacker-controlled scripts running inside these sandboxed iframes can access the autofilled form fields containing sensitive credentials. This occurs because the extension does not sufficiently verify the security context or origin of the iframe before autofilling, allowing malicious actors to bypass sandbox restrictions and exfiltrate credentials. The vulnerability is classified under CWEs 352 (Cross-Site Request Forgery), 640 (Weak Password Recovery Mechanism), and 353 (Missing Support for Integrity Check), indicating issues with insufficient validation and integrity protections. The CVSS v3.1 base score is 7.1 (high), reflecting network attack vector, low attack complexity, no privileges required, user interaction needed, unchanged scope, high confidentiality impact, low integrity impact, and no availability impact. No patches or exploits are currently documented, but the risk is significant given the sensitive nature of password managers and the potential for credential theft. The vulnerability highlights the risks of autofill features in browser extensions when interacting with complex web security policies and sandboxing mechanisms.

For European organizations, this vulnerability poses a significant risk to the confidentiality of stored credentials managed by KeePassXC-Browser. Credential theft can lead to unauthorized access to corporate systems, data breaches, and lateral movement within networks. Organizations relying on KeePassXC-Browser for password management, especially those with employees accessing untrusted or third-party web content embedding sandboxed iframes, are at risk. The attack requires user interaction, such as accepting autofill prompts, which may be exploited via phishing or malicious web content. While integrity and availability impacts are limited, the compromise of credentials can indirectly lead to broader security incidents, including data exfiltration and operational disruption. Given the widespread use of password managers in Europe and the criticality of protecting authentication data, this vulnerability could facilitate targeted attacks against sectors like finance, government, and critical infrastructure. The lack of known exploits in the wild provides a window for proactive mitigation before active exploitation occurs.

1. Immediately monitor for updates from KeePassXC-Browser and apply patches as soon as they become available to address CVE-2025-65203. 2. Until patches are released, disable autofill features in the extension or configure it to require explicit user approval before filling credentials, especially on sites embedding sandboxed iframes. 3. Implement strict Content Security Policies and iframe sandboxing with restrictive attributes (e.g., disallow scripts or forms) on internal and third-party web applications to reduce exposure. 4. Educate users about the risks of autofilling credentials on untrusted or unknown websites and encourage cautious behavior regarding autofill prompts. 5. Employ network monitoring and anomaly detection to identify unusual outbound traffic patterns that may indicate credential exfiltration attempts. 6. Consider alternative password management solutions with more robust iframe and CSP handling until this vulnerability is resolved. 7. Conduct regular security assessments and penetration tests focusing on browser extension interactions with complex web security controls to identify similar risks.