CVE-2025-65203 is a security vulnerability identified in the KeePassXC-Browser extension up to version 1.9.9.2. The vulnerability involves the autofill or prompt-to-fill functionality of stored credentials into web documents that are rendered within iframes subject to browser-enforced Content Security Policy (CSP) directives and sandbox attributes. Normally, sandbox attributes and CSPs are designed to isolate iframe content and restrict script capabilities to prevent malicious code from accessing sensitive data. However, in this case, the KeePassXC-Browser extension improperly allows autofilling or prompting to fill credentials into these sandboxed iframes. This means that attacker-controlled scripts running inside such sandboxed iframes can access the autofilled form fields and exfiltrate the credentials to an external server. The vulnerability undermines the security model of sandboxed iframes and CSPs, which are commonly used to embed third-party or untrusted content safely. The technical root cause appears to be insufficient validation or context checking by the extension before autofilling credentials, failing to recognize the sandboxed environment as untrusted. There are no patches or fixes currently linked, and no known exploits have been reported in the wild. The vulnerability was reserved on November 18, 2025, and published on December 17, 2025. No CVSS score has been assigned yet, but the nature of the vulnerability suggests a high severity due to the direct compromise of credential confidentiality. The affected versions are not explicitly listed beyond up to 1.9.9.2. This vulnerability is particularly concerning for users who embed untrusted content in sandboxed iframes and rely on KeePassXC-Browser for credential management, as it allows attackers to bypass browser security mechanisms and steal sensitive login information.

The primary impact of CVE-2025-65203 is the compromise of user credentials managed by KeePassXC-Browser. For European organizations, this can lead to unauthorized access to corporate accounts, internal systems, and sensitive data if attackers exploit malicious iframe content embedded in internal or external web applications. The breach of credential confidentiality can facilitate lateral movement within networks, data exfiltration, and potential financial or reputational damage. Since the vulnerability bypasses CSP and iframe sandbox protections, it undermines a critical layer of web security, increasing the attack surface for phishing or drive-by attacks. Organizations using web portals or internal tools that embed third-party content in sandboxed iframes are at particular risk. The lack of known exploits currently reduces immediate risk but does not diminish the urgency for mitigation given the ease of exploitation by attacker-controlled scripts. The impact on availability and integrity is indirect but possible if attackers leverage stolen credentials to disrupt services or alter data. Overall, this vulnerability threatens the confidentiality pillar of security and could have widespread consequences if exploited in environments with high usage of KeePassXC-Browser.

To mitigate CVE-2025-65203, European organizations should take the following specific actions: 1) Disable or restrict autofill functionality of KeePassXC-Browser in sandboxed iframe contexts by configuring extension settings or applying custom policies if supported. 2) Monitor and audit web applications that embed third-party content in sandboxed iframes to ensure they do not expose users to attacker-controlled scripts. 3) Apply strict update management to KeePassXC-Browser to promptly install patches once available. 4) Educate users about the risks of autofilling credentials on untrusted or embedded web content and encourage manual credential entry in suspicious contexts. 5) Employ Content Security Policies that limit iframe sources and script execution to trusted domains only, reducing the chance of malicious iframe injection. 6) Consider using additional browser security extensions or endpoint protections that detect and block suspicious iframe activity. 7) Conduct penetration testing and security reviews focusing on iframe usage and credential autofill behavior. These measures go beyond generic advice by focusing on the specific interaction between KeePassXC-Browser autofill and sandboxed iframe environments.