CVE-2012-1956 in Firefox
Summary
by MITRE
Mozilla Firefox before 15.0, Thunderbird before 15.0, and SeaMonkey before 2.12 do not prevent use of the Object.defineProperty method to shadow the location object (aka window.location), which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via vectors involving a plugin.
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Analysis
by VulDB Data Team • 03/27/2021
This vulnerability exists in Mozilla Firefox versions prior to 15.0, Thunderbird versions prior to 15.0, and SeaMonkey versions prior to 2.12 where the Object.defineProperty method can be exploited to shadow the location object. The flaw allows attackers to manipulate the window.location object through JavaScript, creating a dangerous security condition that enables cross-site scripting attacks. This vulnerability specifically targets the browser's object model handling and represents a significant weakness in the security architecture of these applications.
The technical exploitation occurs when malicious code uses the Object.defineProperty method to override or shadow the location object within the browser's JavaScript context. This method allows developers to define new properties or modify existing ones with specific attributes, including configurable and writable flags. When an attacker can make the location object writable or configurable, they can effectively manipulate the browser's navigation behavior and redirect users to malicious sites. The vulnerability is particularly dangerous because it leverages legitimate JavaScript functionality to create an attack vector that bypasses normal security restrictions.
The operational impact of this vulnerability is severe as it significantly lowers the barrier for conducting cross-site scripting attacks. Attackers can craft malicious plugins or web pages that exploit this weakness to inject malicious JavaScript code that executes in the context of the victim's browser session. The shadowing of the location object means that normal security checks and validation mechanisms can be circumvented, allowing attackers to perform unauthorized navigation, steal session cookies, or redirect users to phishing sites. This vulnerability directly impacts the browser's security model and can lead to complete session hijacking or data exfiltration.
The vulnerability aligns with CWE-79, which describes Cross-Site Scripting flaws, and represents a specific implementation weakness in how browser security contexts handle object property definitions. From an ATT&CK perspective, this vulnerability maps to T1059.007 for JavaScript execution and T1566 for phishing attacks that leverage XSS to redirect users. The attack chain typically involves delivering malicious content through compromised websites or browser plugins that exploit this vulnerability to gain unauthorized control over browser navigation and user sessions.
Organizations should immediately update to patched versions of Firefox 15.0, Thunderbird 15.0, and SeaMonkey 2.12 to address this vulnerability. Administrators should also implement additional security measures such as content security policies, regular security audits of browser plugins, and user education about recognizing suspicious website behavior. Network-level protections including web application firewalls and browser security extensions can provide additional layers of defense against exploitation attempts. The fix implemented in the patched versions ensures that the location object cannot be modified through the Object.defineProperty method, restoring proper security boundaries within the browser's JavaScript execution environment.