CVE-2026-74979 in Firefox
Summary
by MITRE • 08/18/2026
Mitigation bypass in the Add-ons Manager component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified security issue represents a critical failure in access control mechanisms within the Mozilla Firefox browser, specifically targeting the Add-ons Manager subsystem. This flaw allows an attacker to circumvent intended mitigation strategies that are designed to restrict how extensions interact with the browser's core functionality and user data. In modern web browsers, add-on managers serve as gatekeepers for third-party software integration, enforcing strict permission models to prevent malicious or poorly coded extensions from compromising system integrity. The existence of a bypass in this component indicates that the validation logic governing extension installation, activation, or privilege escalation contains logical gaps that can be exploited by an adversary with local access or through crafted web content.
From a technical perspective, vulnerabilities in add-on management systems often stem from improper enforcement of security policies during the initialization phase of extensions or when handling manifest files. The Add-ons Manager is responsible for verifying digital signatures, checking permission scopes, and ensuring that requested privileges align with user consent. A bypass suggests that these checks can be manipulated to grant elevated permissions without proper authorization. This could involve tricking the browser into loading an unsigned extension as if it were signed, or exploiting race conditions in the policy application process where security restrictions are not yet fully enforced when malicious code executes. Such flaws undermine the fundamental trust model of the browser ecosystem, allowing potentially harmful scripts to access sensitive APIs that should remain restricted to trusted entities.
The operational impact of this vulnerability is severe, as it directly compromises user privacy and system security. An attacker exploiting this flaw could install rogue extensions or modify existing ones to exfiltrate browsing history, capture credentials stored in password managers, monitor network traffic for session hijacking, or inject malicious content into web pages viewed by the victim. Because add-ons operate with high privileges within the browser context, a successful exploitation can lead to full compromise of the user's online identity and potentially facilitate further attacks on connected systems if remote access capabilities are present. The risk is amplified in enterprise environments where centralized policy management relies on these controls to maintain compliance and security standards across all endpoints.
This type of vulnerability aligns with CWE-284, which describes Improper Access Control, as the core issue lies in the failure to properly restrict actions based on user identity or role. It also maps to MITRE ATT&CK techniques related to browser extension abuse, such as T1505.003 (Web Shell: Browser Extension) and potentially T1059.007 (Command and Scripting Interpreter: JavaScript), depending on the specific exploitation vector used by an attacker. These frameworks highlight how attackers leverage trusted software components to establish persistence or execute arbitrary code, bypassing traditional perimeter defenses that do not monitor internal browser behavior closely enough.
To mitigate this risk, users must ensure they are running Firefox version 154 or later, as well as the Extended Support Release (ESR) version 153.1 or newer, which contain the necessary patches to close these logical gaps in the Add-ons Manager. Administrators should enforce strict extension whitelisting policies and disable automatic installation of add-ons where possible to reduce the attack surface. Regular auditing of installed extensions is also recommended to detect any unauthorized modifications that may have occurred prior to patching. Additionally, keeping all browser components updated ensures that known exploitation techniques are neutralized before they can be leveraged in targeted attacks against organizational infrastructure or individual users.