CVE-2018-6096 in Chrome
Summary
by MITRE
A JavaScript focused window could overlap the fullscreen notification in Fullscreen in Google Chrome prior to 66.0.3359.117 allowed a remote attacker to obscure the full screen warning via a crafted HTML page.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/23/2023
The vulnerability identified as CVE-2018-6096 represents a critical security flaw in Google Chrome's handling of fullscreen notifications and JavaScript window management. This issue specifically affected Chrome versions prior to 66.0.3359.117 and exploited a design weakness in how the browser rendered fullscreen interfaces. The flaw enabled remote attackers to manipulate the visual hierarchy of browser elements, creating a scenario where malicious JavaScript could position overlay windows in front of critical fullscreen notifications. This vulnerability falls under the CWE-124 weakness category, which deals with improper handling of buffer access in web applications, and more specifically relates to CWE-611 which addresses improper access control in web environments.
The technical implementation of this vulnerability relied on the browser's failure to properly enforce the z-index stacking order between fullscreen notifications and JavaScript-generated windows. When a user navigated to a crafted HTML page, the malicious code could create a window element that would appear above the fullscreen warning notification, effectively obscuring important security alerts. This occurred because Chrome's fullscreen API did not adequately distinguish between legitimate browser interface elements and user-generated content when determining visual priority. The attack vector required no user interaction beyond visiting the malicious webpage, making it particularly dangerous as it could be exploited through phishing campaigns or compromised websites.
The operational impact of CVE-2018-6096 was significant as it undermined the fundamental security model that browsers employ to protect users from malicious activities. Fullscreen notifications serve as critical security warnings that alert users to potentially dangerous website behavior, such as attempts to access sensitive system resources or perform unauthorized actions. When these warnings became obscured by crafted JavaScript windows, users might unknowingly proceed with actions that could compromise their security. The vulnerability created a window of opportunity for attackers to perform phishing attacks, social engineering campaigns, or malicious software installations without users being aware of the security risks. This aligns with ATT&CK technique T1059.007 which covers JavaScript-based attacks and T1133 which addresses screen capture and notification manipulation.
Mitigation strategies for this vulnerability centered around immediate browser updates and user education. Google released Chrome version 66.0.3359.117 which addressed the issue by implementing stricter enforcement of the z-index hierarchy between fullscreen notifications and user-generated content. Organizations should have implemented immediate patch management protocols to ensure all affected systems received the update. Additionally, browser security policies should have been reviewed to ensure that fullscreen notifications maintained their proper visual precedence over all other interface elements. The vulnerability highlighted the importance of maintaining proper separation between browser security interfaces and user-controlled content, a principle that aligns with security frameworks such as the OWASP Top Ten and NIST cybersecurity guidelines for web application security.