CVE-2020-6475 in Chrome
Summary
by MITRE
Incorrect implementation in full screen in Google Chrome prior to 83.0.4103.61 allowed a remote attacker to spoof security UI via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2020-6475 represents a critical security flaw in Google Chrome's implementation of full screen mode functionality. This issue affected Chrome versions prior to 83.0.4103.61 and stems from improper handling of security user interface elements during full screen transitions. The flaw specifically manifests when a malicious actor crafts a specially designed HTML page that exploits the browser's failure to properly validate and display security warnings during fullscreen operations.
The technical implementation error occurs within Chrome's rendering engine where the security UI elements fail to maintain their integrity when transitioning to full screen mode. This allows attackers to manipulate the display of security warnings and other protective measures, effectively creating a deceptive environment that can fool users into trusting malicious content. The vulnerability is classified under CWE-284 which deals with improper access control, specifically in the context of user interface security elements. The flaw demonstrates a classic case of insufficient validation of user interface states during application transitions, where the browser fails to properly enforce security boundaries.
Operationally, this vulnerability poses significant risks to user security as it enables man-in-the-middle attacks and phishing attempts. Attackers can craft HTML pages that, when viewed in full screen mode, suppress or alter security warnings that would normally alert users to potential threats. This creates a false sense of security for users who may unknowingly interact with malicious content or provide sensitive information. The attack vector requires only a victim to view a specially crafted webpage, making it particularly dangerous in scenarios involving social engineering or targeted attacks. The vulnerability directly aligns with ATT&CK technique T1059 which involves executing malicious code through web-based interfaces, and T1566 which covers social engineering through deceptive user interfaces.
Mitigation strategies for CVE-2020-6475 primarily focus on immediate browser updates to versions 83.0.4103.61 and later where the implementation has been corrected. Organizations should ensure all Chrome installations are updated promptly and implement browser hardening measures including disabling unnecessary browser features and maintaining strict content security policies. Additionally, user education regarding the importance of verifying security warnings and avoiding suspicious websites remains crucial. The fix implemented by Google addresses the core issue by ensuring proper validation of security UI elements during full screen transitions and maintaining consistent display of security warnings regardless of the browser's display mode. Security teams should monitor for any potential exploitation attempts and consider implementing network-level protections such as web application firewalls to detect and block malicious HTML content that attempts to exploit similar vulnerabilities.