CVE-2009-2654 in Firefox
Summary
by MITRE
Mozilla Firefox before 3.0.13, and 3.5.x before 3.5.2, allows remote attackers to spoof the address bar, and possibly conduct phishing attacks, via a crafted web page that calls window.open with an invalid character in the URL, makes document.write calls to the resulting object, and then calls the stop method during the loading of the error page.
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Analysis
by VulDB Data Team • 12/23/2024
This vulnerability represents a sophisticated browser security flaw that undermines user trust and exposes individuals to targeted phishing attacks. The issue affects Mozilla Firefox versions prior to 3.0.13 and 3.5.x versions before 3.5.2, creating a window of opportunity for attackers to manipulate the browser's address bar display. The vulnerability stems from how Firefox handles window.open operations when presented with malformed URLs containing invalid characters, which triggers unexpected behavior in the browser's rendering engine.
The technical exploitation involves a carefully crafted web page that leverages the window.open function with specifically constructed invalid characters in the URL parameter. When the browser attempts to load this malformed URL, it generates an error page that the attacker can manipulate through subsequent document.write operations targeting the window object returned by window.open. The critical aspect occurs when the attacker calls the stop method during the error page loading process, which interferes with the browser's normal address bar update mechanisms. This interference allows the malicious page to display a false address bar that appears to show a legitimate website URL while actually directing users to a fraudulent destination.
The operational impact of this vulnerability extends beyond simple address bar spoofing to enable sophisticated phishing campaigns that can deceive users who rely on visual cues to verify website authenticity. Users may be tricked into believing they are visiting a trusted website when they are actually interacting with a malicious page that has successfully bypassed the browser's security mechanisms. This vulnerability directly relates to CWE-200, which addresses information exposure, and more specifically to CWE-20, which deals with input validation issues. The attack vector aligns with ATT&CK technique T1056.001, which covers input injection attacks, and T1566, which covers phishing techniques that exploit browser vulnerabilities.
The security implications are particularly severe because address bar spoofing is one of the most effective methods for conducting successful phishing attacks, as users often trust the visual indicators provided by the browser interface. The vulnerability demonstrates the critical importance of proper input validation and error handling in browser implementations, as even malformed URLs should not be allowed to compromise the browser's security model. Organizations and individuals using affected Firefox versions face significant risk, as this vulnerability can be exploited without requiring any special privileges or user interaction beyond visiting a malicious website. The fix implemented by Mozilla involved strengthening the validation of URLs passed to window.open functions and ensuring that error page loading does not interfere with the proper display of the actual navigation address.
This vulnerability highlights the ongoing challenge of maintaining browser security in complex software environments where multiple layers of functionality must interact seamlessly while preserving security boundaries. The attack demonstrates how seemingly minor implementation details in URL handling and error display can create significant security weaknesses that can be exploited for malicious purposes. Security researchers and developers must remain vigilant about such edge cases in browser implementations, as they can provide attackers with powerful methods to bypass user security expectations and trust mechanisms that are fundamental to web browsing security. The vulnerability serves as a reminder that browser security is not just about protecting against traditional exploits, but also about maintaining the integrity of user interface elements that users depend upon for security decisions.