CVE-2010-2264 in Safari
Summary
by MITRE
The Cascading Style Sheets (CSS) implementation in WebKit in Apple Safari before 5.0 on Mac OS X 10.5 through 10.6 and Windows, and before 4.1 on Mac OS X 10.4, does not properly handle the :visited pseudo-class, which allows remote attackers to obtain sensitive information about visited web pages via a crafted HTML document.
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Analysis
by VulDB Data Team • 05/26/2025
The vulnerability described in CVE-2010-2264 represents a significant security flaw in the WebKit rendering engine used by Apple Safari browsers across multiple operating systems. This issue specifically targets the implementation of CSS pseudo-classes, particularly the :visited selector, which is designed to style links that users have previously visited. The flaw arises from how Safari handles the interaction between CSS styling and the browser's internal tracking of visited links, creating an unintended information leakage mechanism that could be exploited by malicious actors.
The technical root cause of this vulnerability stems from the improper handling of the :visited pseudo-class in WebKit's CSS engine. When a web page contains a CSS rule that uses the :visited selector, the browser should only apply styling to links that the user has actually visited. However, the implementation in affected Safari versions failed to properly isolate this functionality, allowing attackers to craft HTML documents that could determine whether specific links had been visited by observing the visual styling applied to them. This behavior violates fundamental security principles of browser isolation and user privacy protection, as it creates a side-channel attack vector that can be exploited to infer user browsing history.
The operational impact of this vulnerability is substantial, as it enables remote attackers to perform privacy reconnaissance attacks against users of affected Safari versions. An attacker could construct malicious web pages that, when visited by a user, would reveal which websites they have previously accessed through the browser's visited link styling. This information disclosure could potentially expose sensitive personal data, including medical websites, financial services, or other confidential resources that users prefer to keep private. The vulnerability affects users across multiple operating systems including Mac OS X 10.5 through 10.6 and Windows platforms, making it a widespread concern for Safari users during that time period. According to CWE classification, this represents a weakness in the security model of the browser's CSS handling mechanism, specifically related to information exposure through side channels.
The exploitability of this vulnerability aligns with techniques described in various ATT&CK frameworks under the information gathering and reconnaissance phases, where adversaries seek to understand user behavior and browsing patterns. The attack vector typically involves hosting malicious web content that leverages CSS properties to determine visited status, making it particularly dangerous because it operates entirely within the browser's rendering engine without requiring any additional permissions or user interaction beyond visiting the malicious page. Security researchers have documented similar vulnerabilities in other browsers, highlighting the need for comprehensive privacy protection mechanisms in CSS implementations. Organizations and users should have implemented immediate mitigations including browser updates to patched versions, while security teams needed to monitor for exploitation attempts and consider implementing network-level protections against known malicious domains. The vulnerability ultimately demonstrated the critical importance of maintaining strict isolation between different browser components and ensuring that CSS functionality does not inadvertently compromise user privacy or security boundaries, establishing a precedent for more rigorous security testing of web rendering engines and their CSS implementations.