CVE-2023-5729 in Firefox
Summary
by MITRE • 10/25/2023
A malicious web site can enter fullscreen mode while simultaneously triggering a WebAuthn prompt. This could have obscured the fullscreen notification and could have been leveraged in a spoofing attack. This vulnerability affects Firefox < 119.
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Analysis
by VulDB Data Team • 11/15/2023
This vulnerability represents a sophisticated browser security flaw that exploits the interaction between fullscreen mode and WebAuthn authentication prompts within the Firefox browser. The issue arises from the improper handling of concurrent user interface elements that can create confusion and potential attack vectors for malicious actors. When a malicious website simultaneously triggers both fullscreen mode and a WebAuthn authentication request, the browser's user interface management fails to properly display the fullscreen notification, creating an opportunity for deceptive user experience manipulation.
The technical implementation flaw stems from Firefox's handling of concurrent browser events where fullscreen mode activation and WebAuthn prompt display interfere with each other's visual presentation. This creates a scenario where users may not receive proper notification about entering fullscreen mode, while simultaneously being prompted for authentication. The vulnerability exists specifically in Firefox versions prior to 119, indicating that the issue was addressed through updates to the browser's event processing and user interface rendering mechanisms. This type of vulnerability aligns with CWE-691, which addresses insufficient control flow management, and CWE-754, concerning the improper handling of security-relevant states.
The operational impact of this vulnerability extends beyond simple user experience degradation to potential security exploitation through social engineering attacks. Attackers could leverage this behavior to create convincing spoofing scenarios where users are unaware they have entered fullscreen mode while simultaneously being prompted for authentication. This dual-layer deception could enable attackers to trick users into providing sensitive information or credentials through WebAuthn prompts that appear legitimate but are actually part of a larger malicious deception. The attack surface is particularly concerning given that WebAuthn is designed for secure authentication and this vulnerability undermines that security foundation.
The threat landscape for this vulnerability aligns with ATT&CK technique T1566, which covers spearphishing with social engineering, and T1071.004, which addresses application layer protocol: dns. The malicious website could use this vulnerability to create convincing phishing scenarios where users are tricked into authenticating through WebAuthn while being unaware of the fullscreen transition. Organizations should prioritize updating Firefox installations to version 119 or later to mitigate this risk. Additional mitigations include implementing browser security policies that restrict fullscreen access, educating users about the potential for deceptive fullscreen transitions, and monitoring for suspicious concurrent browser events that might indicate exploitation attempts.
This vulnerability demonstrates the complexity of modern browser security where seemingly unrelated features can create unexpected interaction points for exploitation. The fix implemented in Firefox 119 likely involved improving the priority handling of fullscreen notifications versus authentication prompts, ensuring that users receive clear and unambiguous feedback about their browser state changes. Security teams should consider this vulnerability as part of broader browser hardening strategies and monitor for similar interaction-based vulnerabilities that could compromise user awareness and security posture. The incident highlights the importance of comprehensive testing for concurrent user interface events and proper state management in browser security implementations.