CVE-2016-9076 in Firefox
Summary
by MITRE
An issue where a "<select>" dropdown menu can be used to cover location bar content, resulting in potential spoofing attacks. This attack requires e10s to be enabled in order to function. This vulnerability affects Firefox < 50.
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Analysis
by VulDB Data Team • 10/04/2022
This vulnerability represents a sophisticated browser-based attack vector that exploits the interaction between HTML form elements and browser user interface components. The flaw specifically targets the Firefox browser's implementation of the e10s (Electrolysis) architecture, which enables multi-process browsing to improve stability and security. The vulnerability occurs when a malicious web page constructs a specially crafted select dropdown menu that can obscure the browser's location bar, creating an environment conducive to phishing and spoofing attacks. This represents a significant breach in browser security boundaries where the rendering engine fails to properly isolate user interface elements from potentially malicious content.
The technical implementation of this vulnerability leverages the unique characteristics of Firefox's e10s architecture where the content process and browser UI process operate in separate processes. When e10s is enabled, a malicious page can manipulate the positioning and layering of HTML elements such that a select dropdown menu can be positioned over the browser's location bar. This allows attackers to display fake URLs or domain names while the actual navigation continues to a malicious destination. The vulnerability stems from insufficient validation of element positioning and z-index handling between different browser processes, creating a window where user interface elements can be overlaid with deceptive content.
The operational impact of this vulnerability extends beyond simple phishing attempts to encompass a broader range of spoofing attacks that can deceive users into believing they are visiting legitimate websites. Attackers can exploit this flaw to display fake login forms, banking interfaces, or other sensitive application interfaces while simultaneously redirecting users to malicious sites. The attack requires the victim to have e10s enabled, which was the default configuration in Firefox 49 and earlier versions, making it particularly dangerous for users who had not yet upgraded to newer releases. This vulnerability directly impacts user trust in browser security mechanisms and represents a failure in browser sandboxing principles that should prevent content from manipulating user interface elements.
Security mitigations for this vulnerability primarily involve updating to Firefox version 50 or later where the issue has been resolved through improved process isolation and element positioning controls. Browser vendors should implement additional checks to prevent overlay attacks by enforcing stricter boundaries between content rendering and user interface components. The fix typically involves modifying how select elements and other HTML form controls interact with browser UI elements, particularly in multi-process environments. Organizations should ensure their Firefox installations are updated to the patched versions and consider implementing additional security measures such as browser hardening configurations that disable unnecessary features. This vulnerability aligns with CWE-691, which addresses insufficient control of a resource through a mechanism that allows a user to manipulate the resource in unexpected ways. The attack pattern corresponds to techniques described in the ATT&CK framework under the T1056 category for Input Injection, specifically targeting user interface manipulation to deceive users into providing sensitive information.