CVE-2020-6478 in Chrome
Summary
by MITRE
Inappropriate 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-2020-6478 represents a critical security flaw in Google Chrome's implementation of full screen functionality that existed prior to version 83.0.41. This issue falls under the category of improper implementation in security-critical UI components, specifically affecting how Chrome handles full screen mode transitions and user interface elements. The flaw enables remote attackers to manipulate the browser's security user interface through carefully crafted HTML content, potentially leading to deceptive security prompts and misleading user experiences. Such vulnerabilities are particularly dangerous because they exploit the trust users place in browser security indicators and can be leveraged to bypass security mechanisms that protect against malicious activities.
The technical implementation flaw stems from Chrome's inadequate validation and rendering of security UI elements during full screen transitions. When a web page attempts to enter full screen mode, Chrome displays security prompts to inform users about the change and to confirm their intent to proceed. However, the vulnerability allows attackers to craft HTML pages that can manipulate these security UI elements, causing them to display misleading information or to be bypassed entirely. This improper handling of UI rendering during full screen transitions creates an attack surface where malicious actors can exploit the browser's security model by injecting crafted content that appears to be legitimate security notifications. The vulnerability is classified under CWE-693, which deals with protection mechanism failures, specifically in the context of user interface security controls.
The operational impact of CVE-2020-6478 extends beyond simple user interface manipulation to potentially enable more sophisticated attacks that could deceive users into performing actions they would not normally undertake. Attackers could exploit this vulnerability to create convincing phishing scenarios where security warnings appear to originate from trusted sources, or to bypass user consent mechanisms that are crucial for protecting against malicious activities. The vulnerability particularly affects users who frequently interact with web applications that utilize full screen functionality, as the attack surface is broad and can be easily exploited through standard web browsing activities. This makes it especially dangerous in enterprise environments where users may be less cautious about full screen transitions and more likely to interact with potentially malicious content.
Mitigation strategies for CVE-2020-6478 primarily focus on updating Chrome to version 83.0.41 or later, which contains the necessary patches to address the improper UI implementation. Organizations should implement comprehensive update policies to ensure all Chrome installations are current with the latest security patches. Additionally, browser security configurations can be enhanced by implementing stricter content security policies and disabling unnecessary full screen permissions for untrusted websites. Network administrators should monitor for suspicious web content and consider implementing web filtering solutions that can detect and block potentially malicious full screen transition attempts. The vulnerability demonstrates the importance of maintaining current browser versions and following security best practices as outlined in the ATT&CK framework under the T1059 category, which covers defense evasion techniques that attackers might employ through UI manipulation. Organizations should also consider user education programs that emphasize the importance of being cautious when encountering full screen prompts and verifying the legitimacy of security warnings before taking any action.