CVE-2005-0145 in Firefox
Summary
by MITRE
Firefox before 1.0 does not properly distinguish between user-generated and synthetic click events, which allows remote attackers to use Javascript to bypass the file download prompt when the user uses the Alt-click feature.
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Analysis
by VulDB Data Team • 06/05/2019
The vulnerability described in CVE-2005-0145 represents a significant security flaw in the Firefox web browser version 1.0 and earlier, specifically related to how the browser handles click event processing. This issue stems from Firefox's inability to properly differentiate between legitimate user-generated click events and synthetic events that are programmatically generated through javascript code. The flaw exploits a fundamental weakness in the browser's event handling system where the security mechanisms designed to protect users during file downloads fail when confronted with malicious javascript code that can simulate user interactions.
The technical implementation of this vulnerability allows remote attackers to craft javascript code that can generate synthetic click events which appear to originate from user interactions. When users employ the Alt-click feature to download files, the browser's security model incorrectly treats these synthetic events as legitimate user actions, thereby bypassing the intended file download prompts that are meant to warn users about potentially dangerous downloads. This bypass mechanism specifically targets the browser's security model for file handling and download management, creating a scenario where users can be tricked into downloading files without proper awareness or consent.
The operational impact of this vulnerability is substantial as it directly undermines user security and trust in the browser's protective mechanisms. Attackers can exploit this weakness to deliver malicious files without user knowledge or consent, potentially leading to malware infections, data theft, or other security breaches. The vulnerability affects users who have the Alt-click feature enabled, which was a common and convenient method for downloading files in the pre-1.0 Firefox versions. This attack vector represents a form of social engineering combined with browser exploitation, making it particularly dangerous as it leverages legitimate user workflows to execute malicious code.
This vulnerability aligns with several cybersecurity frameworks and threat models, particularly relating to CWE-254, which addresses security weaknesses in event handling and input validation. The issue also connects to ATT&CK technique T1059.007, which involves the use of javascript for execution, and T1203, which covers social engineering techniques. The flaw demonstrates how seemingly minor implementation details in browser security can create significant attack surfaces, particularly when dealing with user interaction models and event propagation. The vulnerability highlights the importance of proper event validation and the need for browsers to maintain strict separation between user-generated and programmatic events to prevent such bypasses.
Mitigation strategies for this vulnerability required users to either disable the Alt-click feature or upgrade to Firefox version 1.0 or later, where the security flaw was addressed through improved event handling mechanisms. Browser vendors should implement robust event discrimination systems that can properly identify and handle synthetic events while maintaining the functionality of legitimate user interactions. The fix involved strengthening the browser's security model to ensure that file download prompts are only bypassed when genuine user actions occur, rather than when javascript code attempts to simulate such actions. This vulnerability serves as a critical reminder of the importance of comprehensive event validation in browser security implementations and the necessity of maintaining strict security boundaries between different types of user interactions.