CVE-2007-1091 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 7 allows remote attackers to prevent users from leaving a site, spoof the address bar, and conduct phishing and other attacks via onUnload Javascript handlers.
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Analysis
by VulDB Data Team • 03/15/2021
Microsoft Internet Explorer 7 contained a critical security vulnerability that enabled remote attackers to manipulate browser behavior through malicious javascript execution. This vulnerability specifically exploited the onUnload event handler functionality within the browser's javascript engine, allowing adversaries to create persistent barriers that prevented users from navigating away from compromised web pages. The flaw originated from insufficient validation and sanitization of javascript code executed during page unload events, creating an attack surface that could be leveraged for malicious purposes.
The technical implementation of this vulnerability stemmed from IE7's handling of the onUnload javascript event which was designed to execute code when a user navigated away from a webpage. Attackers could inject malicious javascript code that would trigger upon page unload, causing the browser to display deceptive content or redirect users to fraudulent websites. This mechanism bypassed normal browser security restrictions and allowed attackers to manipulate the user interface in ways that were not intended by the browser's security model. The vulnerability was particularly dangerous because it operated at the browser's core javascript execution layer, making it difficult to detect and prevent through traditional security measures.
The operational impact of CVE-2007-1091 was severe and multifaceted, enabling sophisticated phishing attacks that could completely deceive users about their current location on the internet. Attackers could leverage this vulnerability to spoof the address bar, making it appear as though users were visiting legitimate websites while actually navigating to malicious domains. This capability directly violated fundamental security principles of web browser isolation and user trust, as users could be tricked into entering sensitive information on fraudulent sites. The vulnerability also allowed for persistent site blocking mechanisms that prevented users from escaping compromised pages, creating a captive audience for phishing operations and other malicious activities.
This vulnerability aligns with multiple CWE categories including CWE-200 for information exposure and CWE-352 for cross-site request forgery, as it enabled attackers to manipulate browser behavior and information display. From an ATT&CK framework perspective, the vulnerability corresponds to T1566 for credential access through phishing and T1071 for application layer protocol usage. The attack vector typically involved hosting malicious javascript on compromised websites that would execute when users attempted to navigate away, creating a persistent threat that could be difficult to trace. Organizations using IE7 were particularly vulnerable as the browser lacked proper protections against malicious onUnload handlers, making it a prime target for attackers seeking to conduct large-scale phishing campaigns.
The recommended mitigations for this vulnerability included immediate deployment of Microsoft security patches that addressed the javascript execution handling during page unload events. Browser vendors should have implemented stricter javascript sandboxing mechanisms and enhanced validation of onUnload event handlers. Users were advised to disable javascript execution when not required, utilize browser security extensions, and maintain updated browser versions. Network administrators needed to implement web filtering solutions that could detect and block malicious javascript patterns. The vulnerability highlighted the importance of proper event handler validation and the need for comprehensive browser security models that account for all possible javascript execution paths. Organizations should have conducted security assessments to identify systems running vulnerable versions of IE7 and prioritized immediate remediation efforts to prevent exploitation.