CVE-2011-3866 in Firefox
Summary
by MITRE
Mozilla Firefox before 7.0 and SeaMonkey before 2.4 do not properly restrict availability of motion data events, which makes it easier for remote attackers to read keystrokes by leveraging JavaScript code running in a background tab.
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Analysis
by VulDB Data Team • 11/20/2021
The vulnerability described in CVE-2011-3866 represents a significant security flaw in web browser implementations that affects Mozilla Firefox versions prior to 7.0 and SeaMonkey versions prior to 2.4. This issue stems from improper restrictions on motion data events, creating an unintended information leakage mechanism that could be exploited by malicious actors. The flaw specifically targets the browser's handling of background tab JavaScript execution, allowing remote attackers to potentially capture keystroke data through sophisticated code manipulation. This vulnerability demonstrates the complex security challenges that arise when implementing event handling systems in modern web browsers where multiple tabs and background processes interact with JavaScript code.
The technical root cause of this vulnerability lies in the insufficient validation and restriction of motion data events within the browser's JavaScript execution environment. When JavaScript code runs in background tabs, the browser should properly isolate these processes to prevent unauthorized access to sensitive data. However, the implementation failed to adequately restrict access to motion events that could be leveraged to infer user input patterns. This weakness creates a pathway for attackers to monitor and potentially capture keystrokes through the motion data event system, which should normally be restricted to prevent such cross-tab information leakage. The vulnerability operates under the principle that background tab processes should not have access to foreground tab data, yet the motion event handling mechanism allowed this boundary to be crossed.
The operational impact of CVE-2011-3866 is substantial as it enables sophisticated keystroke logging attacks that could compromise user privacy and security. Attackers could exploit this vulnerability to capture sensitive information such as passwords, credit card numbers, and personal communications while users browse other websites or applications. The vulnerability is particularly dangerous because it operates silently in the background without user awareness, making detection extremely difficult. The attack vector requires only a malicious website that can execute JavaScript code, making it accessible through typical web browsing activities. This vulnerability directly relates to the CWE-200 weakness category, which encompasses information exposure problems, and aligns with ATT&CK technique T1056.001 for input injection attacks that leverage browser-based information gathering.
Mitigation strategies for this vulnerability involve immediate browser updates to versions that properly address the motion data event restrictions. Users should ensure they are running Firefox 7.0 or later and SeaMonkey 2.4 or later, where the implementation has been corrected to properly isolate background tab JavaScript execution from foreground tab data access. Additionally, security-conscious organizations should implement browser hardening policies that limit the execution of untrusted JavaScript code, particularly in environments where sensitive data processing occurs. Network administrators should consider deploying web content filters and monitoring systems that can detect suspicious JavaScript behavior patterns. The vulnerability serves as a reminder of the importance of proper event handling isolation in browser security models and demonstrates how seemingly minor implementation flaws can create significant attack vectors for information leakage and keystroke capture attacks.