CVE-2007-1095 in Firefox
Summary
by MITRE
Mozilla Firefox before 2.0.0.8 and SeaMonkey before 1.1.5 do not properly implement JavaScript onUnload handlers, which allows remote attackers to run certain JavaScript code and access the location DOM hierarchy in the context of the next web site that is visited by a client.
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Analysis
by VulDB Data Team • 03/16/2021
The vulnerability described in CVE-2007-1095 represents a critical cross-site scripting and information disclosure flaw in Mozilla Firefox versions prior to 2.0.0.8 and SeaMonkey versions prior to 1.1.5. This issue stems from improper implementation of JavaScript onUnload event handlers which creates a security boundary violation in the browser's JavaScript execution environment. The flaw allows remote attackers to execute arbitrary JavaScript code in the context of subsequent websites visited by the user, effectively enabling a form of persistent cross-site scripting that can persist across different domains and potentially compromise user sessions.
The technical implementation of this vulnerability occurs through the flawed handling of the onUnload event in JavaScript within the browser's rendering engine. When a user visits a malicious website that contains specifically crafted JavaScript code designed to exploit this flaw, the onUnload handler is improperly processed in a way that allows the code to persist in memory or execution context. This persistence enables the malicious script to execute when the user navigates to a different website, effectively hijacking the browser's JavaScript execution environment and gaining access to the Document Object Model hierarchy of the new site. The vulnerability essentially creates a bridge between different security contexts, allowing code execution that bypasses normal cross-origin security restrictions.
From an operational impact perspective, this vulnerability represents a significant threat to user privacy and session security. Attackers can leverage this flaw to steal session cookies, access user data, or perform actions on behalf of the user across different domains. The vulnerability is particularly dangerous because it operates across different security boundaries, meaning that a malicious site can affect subsequent sites visited by the user. This creates a persistent threat vector that can remain active even after the initial malicious site is closed, potentially allowing for extended surveillance or exploitation. The attack requires minimal user interaction beyond normal browsing behavior, making it particularly effective for widespread exploitation.
The vulnerability maps to CWE-938, which specifically addresses the weakness of insufficiently protected credentials or information, and aligns with ATT&CK technique T1059.007 for JavaScript execution. Mitigation strategies should focus on immediate browser updates to versions that properly implement JavaScript onUnload handlers and enforce proper security boundaries between different browsing contexts. Additionally, users should be educated about the importance of keeping browsers updated and avoiding suspicious websites. Network security controls can help by implementing web filtering and monitoring for suspicious JavaScript behavior, though the fundamental fix requires updating the browser software. Organizations should also consider implementing browser hardening measures and monitoring for potential exploitation attempts through network traffic analysis and endpoint detection systems.