CVE-2025-13013 is a vulnerability identified in Mozilla Firefox and Thunderbird affecting versions prior to Firefox 145, Firefox ESR 140.5, and Thunderbird 145 and 140.5. The flaw is a mitigation bypass in the DOM: Core & HTML component, categorized under CWE-288, which involves authentication bypass via an alternate path or channel. This suggests that the vulnerability allows an attacker to circumvent security mitigations designed to protect the Document Object Model (DOM) from unauthorized manipulation. Exploitation requires no privileges and no authentication but does require user interaction, such as visiting a malicious webpage or opening crafted content. The CVSS 3.1 base score is 6.1 (medium), with vector AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N, indicating network attack vector, low attack complexity, no privileges required, user interaction required, scope changed, and low impact on confidentiality and integrity, with no impact on availability. The scope change (S:C) means the vulnerability affects components beyond the initially vulnerable component, potentially allowing broader impact. No known exploits are reported in the wild, and no patches are linked yet, indicating the vulnerability was recently disclosed. The vulnerability could allow attackers to bypass DOM security mitigations, potentially leading to unauthorized access to sensitive information or manipulation of web content in the browser context. This could be leveraged for phishing, session hijacking, or other attacks that compromise user data confidentiality and integrity. The lack of availability impact reduces the risk of denial-of-service conditions. The vulnerability affects widely used versions of Firefox and Thunderbird, which are popular in both consumer and enterprise environments.

For European organizations, the vulnerability poses a risk primarily to confidentiality and integrity of data accessed or processed via Firefox and Thunderbird clients. Attackers exploiting this flaw could bypass DOM security mitigations, potentially leading to unauthorized access to sensitive information such as session tokens, personal data, or corporate communications. This could facilitate targeted phishing campaigns, credential theft, or unauthorized actions within web applications. Since the vulnerability requires user interaction, the risk is heightened in environments where users frequently access untrusted web content or email attachments. The absence of known exploits reduces immediate risk but does not eliminate it, especially as threat actors may develop exploits post-disclosure. Organizations relying heavily on Firefox and Thunderbird for web browsing and email, including government agencies, financial institutions, and critical infrastructure operators, could face increased exposure. The medium severity suggests a moderate impact, but the scope change indicates potential for broader compromise if chained with other vulnerabilities. Availability is not impacted, so service disruption is unlikely. Overall, the vulnerability could undermine trust in browser-based security controls and lead to data breaches if unmitigated.

1. Apply patches promptly once Mozilla releases updates addressing CVE-2025-13013. Monitor Mozilla security advisories closely for patch availability. 2. Until patches are available, implement strict Content Security Policies (CSP) to restrict the execution of untrusted scripts and reduce DOM manipulation risks. 3. Educate users about the risks of interacting with suspicious links or email attachments, emphasizing caution with unknown sources. 4. Employ browser security extensions or enterprise policies that limit JavaScript execution or sandbox untrusted content. 5. Use network-level protections such as web filtering and email gateways to block access to known malicious sites and phishing emails. 6. Conduct regular security awareness training focused on social engineering and phishing tactics that could exploit this vulnerability. 7. Monitor browser and email client logs for unusual activity that may indicate exploitation attempts. 8. Consider deploying endpoint detection and response (EDR) solutions capable of detecting anomalous browser behaviors. 9. For organizations using Firefox ESR versions, plan coordinated upgrade cycles to minimize exposure to outdated versions. 10. Review and harden internal web applications to minimize reliance on vulnerable browser features and reduce attack surface.