CVE-2015-7187 in Firefox
Summary
by MITRE
The Add-on SDK in Mozilla Firefox before 42.0 misinterprets a "script: false" panel setting, which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via inline JavaScript code that is executed within a third-party extension.
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Analysis
by VulDB Data Team • 06/26/2022
The vulnerability identified as CVE-2015-7187 represents a critical security flaw within the Add-on SDK of Mozilla Firefox versions prior to 42.0. This issue stems from a misinterpretation of the "script: false" panel setting that governs how JavaScript execution is handled within third-party extensions. The flaw allows remote attackers to bypass intended security restrictions and execute malicious inline JavaScript code within the context of extension panels, creating a significant vector for cross-site scripting attacks.
The technical implementation of this vulnerability occurs within the Firefox extension framework where the Add-on SDK is responsible for managing panel behavior and security boundaries. When developers set "script: false" in panel configurations, they expect that JavaScript execution will be disabled or severely restricted within that panel context. However, the flawed implementation fails to properly enforce this restriction, allowing attackers to inject and execute malicious JavaScript code through carefully crafted inline scripts that can manipulate the extension's user interface and potentially access sensitive data.
This vulnerability directly impacts the security model of Firefox extensions by undermining the isolation mechanisms that should protect users from malicious code execution. The operational impact is significant as it enables attackers to exploit legitimate third-party extensions as attack vectors, potentially leading to session hijacking, data theft, or privilege escalation within the browser environment. The vulnerability operates at the intersection of browser security boundaries and extension permissions, creating a pathway for attackers to leverage trusted extension contexts to execute unauthorized code.
The flaw manifests when an attacker crafts malicious inline JavaScript code that gets executed within the context of a third-party extension panel where script execution should be disabled. This creates a persistent threat vector that can be exploited across different extension installations and user environments. The vulnerability is particularly dangerous because it leverages the trust model inherent in browser extensions, where users expect that extensions operate within defined security parameters that prevent arbitrary code execution.
Security professionals should consider this vulnerability in relation to CWE-79, which addresses cross-site scripting flaws, and the ATT&CK framework's techniques for code injection and privilege escalation. The remediation approach requires updating Firefox to version 42.0 or later where the Add-on SDK properly enforces the "script: false" panel setting. Organizations should also implement extension review processes and monitor for malicious extensions that might exploit similar vulnerabilities in older Firefox versions. Additionally, developers should be educated about proper panel configuration practices and the importance of validating extension security boundaries to prevent similar issues in custom extension development.