CVE-2026-117960 in Firefox
Summary
by MITRE • 10/27/2026
Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw resides within the Document Object Model core and HTML components of Mozilla Firefox, representing a critical category of web application vulnerabilities known as DOM-based spoofing. In this context, the vulnerability allows an attacker to manipulate or deceive users regarding the true origin or state of content displayed by the browser. This type of issue typically arises when user-controllable data is written directly into the Document Object Model without adequate sanitization or validation, leading to a discrepancy between what the user perceives and the actual underlying code execution context. The core HTML parsing engine failed to properly enforce boundaries that prevent malicious scripts from masquerading as legitimate content or trusted interfaces, thereby undermining the browser's ability to maintain trust in displayed information.
From a technical perspective, this flaw likely involves improper handling of URL schemes, document titles, or meta tags where attacker-controlled input influences visual rendering without triggering appropriate security checks. By exploiting this weakness, an adversary can craft malicious web pages that display deceptive elements such as fake login prompts, misleading URLs, or counterfeit interface components that appear to originate from a trusted source. This manipulation relies on the browser's default behavior of trusting certain DOM properties for presentation purposes while failing to validate their integrity against injection attacks. The absence of robust checks allows scripts to alter these visual indicators in real-time, creating a convincing illusion of legitimacy that bypasses user skepticism and security warnings designed to detect phishing or malicious activity.
The operational impact of this vulnerability is significant, particularly in environments where users interact with sensitive web applications such as online banking, corporate portals, or email services. Successful exploitation enables sophisticated social engineering attacks by allowing attackers to create highly convincing phishing pages that mimic legitimate sites more effectively than traditional methods. Users may inadvertently submit credentials, personal identifiable information, or financial details to a malicious actor because the visual cues provided by the browser suggest they are on an authentic site. This erosion of trust in the user interface can lead to direct data breaches, unauthorized access to accounts, and potential compromise of downstream systems if session tokens or authentication cookies are harvested through these deceptive interfaces.
This vulnerability aligns with Common Weakness Enumeration standards such as CWE-79 for Improper Neutralization of Input During Web Page Generation which covers cross-site scripting vectors that affect DOM manipulation, and potentially CWE-20 for improper input validation when the browser fails to reject malformed or malicious structural elements. In terms of the MITRE ATT&CK framework, this behavior corresponds to techniques involving Client-Side Phishing where attackers use social engineering combined with technical exploitation to deceive users into performing actions detrimental to their security posture. The specific mechanism falls under sub-techniques that involve manipulating browser UI components to hide malicious intent or mimic trusted entities, leveraging the user's reliance on visual indicators for trust decisions.
Mitigation strategies primarily rely on the vendor-provided patch released in Firefox version 159 and Firefox Extended Support Release (ESR) version 153.6. Organizations must ensure that all instances of Firefox are updated to these versions or later to eliminate the underlying code flaws responsible for the DOM manipulation weakness. For environments where immediate patching is not feasible, compensating controls should be implemented such as deploying Content Security Policy headers to restrict script execution and prevent unauthorized modifications to critical DOM elements. Additionally, user awareness training focused on verifying URL authenticity through certificate details rather than relying solely on visual page layout can reduce susceptibility to this type of deception. Regular security audits focusing on input validation in web applications developed internally or hosted by third parties are also recommended to minimize the attack surface available for exploiting similar vulnerabilities in other browsers or platforms.