CVE-2025-5267 is a clickjacking vulnerability identified in Mozilla Firefox and Thunderbird products prior to versions 139 and ESR versions prior to 128.11. Clickjacking is a technique where an attacker tricks a user into clicking on something different from what the user perceives, potentially revealing sensitive information or performing unintended actions. In this specific vulnerability, an attacker could craft a malicious webpage that overlays or disguises UI elements to deceive the user into leaking saved payment card details stored in the browser or email client. The vulnerability affects Firefox versions below 139, Firefox ESR below 128.11, Thunderbird below 139, and Thunderbird ESR below 128.11. The CVSS v3.1 base score is 5.4 (medium severity), with vector AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N, indicating that the attack can be performed remotely over the network without privileges but requires user interaction. The impact is limited to confidentiality and integrity of saved payment card data, with no direct impact on availability. No known exploits are currently reported in the wild, and no patches are linked yet, suggesting this is a recently disclosed vulnerability. The underlying weakness is categorized under CWE-1021, which relates to clickjacking. The vulnerability could allow attackers to bypass UI protections and trick users into unintentionally revealing sensitive payment card information, potentially leading to financial fraud or identity theft if exploited successfully. Given the nature of the vulnerability, exploitation requires user interaction and a victim visiting a maliciously crafted webpage or email content. This vulnerability highlights the importance of robust UI security controls and user awareness to prevent social engineering attacks that leverage clickjacking techniques.

For European organizations, this vulnerability poses a moderate risk primarily to end users who store payment card information in Firefox or Thunderbird. Financial institutions, e-commerce platforms, and any organizations relying on Firefox or Thunderbird for business communications or transactions could face indirect risks if their users' payment data is compromised. The leakage of saved payment card details could lead to fraudulent transactions, financial losses, and reputational damage. Organizations handling sensitive payment data must be aware that attackers could leverage this vulnerability to bypass UI protections and extract confidential information without direct system compromise. The impact is heightened in sectors with high online payment volumes or where employees use affected software for business purposes. However, since exploitation requires user interaction and no known exploits are in the wild, the immediate threat level is moderate. Still, European organizations should proactively address this vulnerability to prevent potential targeted attacks, especially given the widespread use of Firefox and Thunderbird across Europe.

1. Update affected software: Organizations and users should promptly update Mozilla Firefox to version 139 or later and Thunderbird to version 139 or later, including ESR versions to 128.11 or later once patches are released. 2. Employ browser security features: Enable and enforce Content Security Policy (CSP) headers and X-Frame-Options to prevent framing and reduce clickjacking risks on internal and external web applications. 3. User awareness training: Educate users about the risks of clickjacking and the importance of avoiding clicking on suspicious or unexpected UI elements, especially on untrusted websites or emails. 4. Use browser extensions or security tools that detect or block clickjacking attempts. 5. Monitor for suspicious activity: Financial and security teams should monitor transaction logs and user reports for signs of fraudulent activity potentially linked to this vulnerability. 6. Limit storage of payment card details in browsers where possible, encouraging use of dedicated secure payment methods or tokenization. 7. For organizations using Thunderbird for email, ensure email clients are updated and consider additional email security controls to prevent malicious content triggering clickjacking. 8. Implement network-level protections such as web filtering to block access to known malicious sites that could host clickjacking attacks.