CVE-2026-92015 in Firefox
Summary
by MITRE • 09/15/2026
Privilege escalation in the WebExtensions component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security issue represents a critical privilege escalation flaw within the WebExtensions subsystem of Mozilla Firefox browsers. This vulnerability allows an attacker with limited permissions to execute code or access resources that are normally restricted to higher-privilege contexts, such as browser internals or other extensions. The root cause typically stems from insufficient validation of extension APIs or improper isolation between different security levels within the browser's architecture. In modern web browsers, WebExtensions operate under a sandboxed environment designed to prevent malicious scripts from accessing sensitive user data or system resources. However, when this boundary is compromised due to logic errors in how permissions are granted or enforced, an attacker can exploit these gaps to bypass intended restrictions and gain elevated access rights within the browser process space.
From a technical perspective, privilege escalation vulnerabilities often arise from race conditions, improper state management, or flawed implementation of content scripts interacting with background pages. In the context of WebExtensions, this might involve manipulating extension APIs in ways that were not anticipated by developers, such as tricking the browser into treating a low-privilege script as if it had high-level administrative capabilities. This could allow an attacker to read cookies from other domains, access local storage belonging to privileged extensions, or even inject malicious code into secure contexts like about:blank pages which are typically protected against cross-origin attacks. The severity of this flaw lies in its potential to undermine the fundamental trust model of the browser, where users rely on isolation mechanisms to protect their privacy and security while browsing untrusted websites.
The operational impact of such a vulnerability is significant for both individual users and enterprise environments relying on Firefox. For end-users, successful exploitation could lead to session hijacking, credential theft, or unauthorized access to personal data stored within the browser profile. In corporate settings where managed extensions are deployed, this flaw could allow malicious actors embedded in legitimate-looking extensions to exfiltrate sensitive organizational information or establish persistence mechanisms that survive browser restarts. The risk is further amplified by the widespread adoption of WebExtensions as a standard for adding functionality to browsers, meaning that any compromise affects not just the core application but also the ecosystem of third-party tools users depend on daily.
To mitigate this vulnerability, it is imperative to apply the latest security patches immediately upon release. Mozilla has addressed this issue in Firefox version 156, as well as specific extended support releases including ESR versions 115.41, 140.16, and 153.3. Organizations should ensure that their update policies are configured to automatically deploy these patches across all endpoints running affected browser versions. Additionally, administrators should review installed extensions for any suspicious behavior or excessive permissions requests, as attackers may attempt to leverage this flaw through maliciously crafted add-ons before the patch is widely deployed. Implementing strict extension whitelisting and monitoring for unusual API calls can provide an additional layer of defense against exploitation attempts targeting unpatched systems.
This vulnerability aligns with common classification standards in cybersecurity frameworks. It corresponds closely to CWE-269, which describes Improper Privilege Management, specifically where a principal is granted more privileges than necessary or intended. Furthermore, the attack vector relates to MITRE ATT&CK techniques involving privilege escalation within software applications, potentially facilitating lateral movement if an attacker gains control over browser processes that have access to other networked resources. Understanding these classifications helps security teams prioritize remediation efforts and align their defensive strategies with industry best practices for managing application-level vulnerabilities. Continuous monitoring of vendor advisories and maintaining up-to-date software configurations remain the most effective defenses against such exploits in production environments.