CVE-2016-1958 in Firefox
Summary
by MITRE
browser/base/content/browser.js in Mozilla Firefox before 45.0 and Firefox ESR 38.x before 38.7 allows remote attackers to spoof the address bar via a javascript: URL.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability described in CVE-2016-1958 represents a significant security flaw in Mozilla Firefox's handling of javascript: URLs within the browser's address bar functionality. This issue affects versions prior to Firefox 45.0 and Firefox ESR 38.x before 38.7, creating a potential avenue for sophisticated phishing attacks and user deception. The flaw resides in the browser/base/content/browser.js file which governs how the browser processes and displays javascript: URLs, specifically failing to properly validate or sanitize these protocol handlers when they appear in the address bar context.
The technical nature of this vulnerability stems from insufficient input validation and sanitization within Firefox's URL processing pipeline. When a javascript: URL is encountered, the browser should properly distinguish between legitimate script execution contexts and potentially malicious spoofing attempts. However, the implementation flaw allows remote attackers to craft javascript: URLs that can manipulate the address bar display, making it appear as though the user is visiting a legitimate website when they are actually interacting with malicious content. This bypasses critical security mechanisms that users rely upon to verify website authenticity, as the address bar becomes a vector for deception rather than a reliable indicator of site legitimacy.
The operational impact of this vulnerability extends beyond simple address bar spoofing, as it fundamentally undermines user trust in the browser's security interface. Attackers can leverage this flaw to create convincing phishing scenarios where the address bar displays fraudulent URLs, potentially tricking users into entering sensitive information or executing malicious actions. This vulnerability aligns with CWE-79, which addresses Cross-Site Scripting (XSS) flaws, as the issue involves improper handling of user-controllable input that can be manipulated to execute unintended code or display misleading information. The attack vector operates through the ATT&CK technique T1059.007 for JavaScript execution, combined with T1566 for credential harvesting through social engineering.
The security implications of this vulnerability are particularly concerning given Firefox's widespread adoption and users' reliance on address bar indicators for site verification. This flaw enables sophisticated phishing campaigns where attackers can create convincing fake banking or e-commerce sites that appear legitimate to users. The vulnerability demonstrates a critical failure in Firefox's security model, where the browser's own address bar protection mechanisms are circumvented by malicious javascript: URLs. Organizations using Firefox should consider immediate remediation through version updates, as the vulnerability represents a direct threat to user security and trust in the browser's interface. The flaw also highlights the importance of proper URL validation and sanitization in web browsers, particularly in contexts where user trust is paramount and security interfaces are involved.