CVE-2002-2437 in Firefox
Summary
by MITRE
The JavaScript implementation in Mozilla Firefox before 4.0, Thunderbird before 3.3, and SeaMonkey before 2.1 does not properly restrict the set of values contained in the object returned by the getComputedStyle method, which allows remote attackers to obtain sensitive information about visited web pages by calling this method.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/13/2019
The vulnerability described in CVE-2002-2437 represents a significant information disclosure flaw in the JavaScript engine implementation of Mozilla Firefox and related applications. This issue specifically affects the getComputedStyle method which is designed to retrieve computed style properties of elements in web documents. The flaw arises from insufficient validation of the values returned by this method, creating a potential avenue for attackers to extract sensitive information about a user's browsing history and visited web pages.
The technical implementation of this vulnerability stems from the improper handling of CSS property values within the getComputedStyle API. When web applications call this method, they expect to receive standardized computed style values that reflect the actual rendering properties of DOM elements. However, the flawed implementation in affected versions allowed certain CSS properties to return values that could be manipulated or inferred to reveal information about the underlying document structure and visited resources. This occurs because the method should only return values that are relevant to the computed style properties but instead exposes additional metadata that can be exploited.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable sophisticated tracking and profiling attacks. Attackers can leverage this flaw to determine whether specific web pages have been visited by analyzing the responses from getComputedStyle calls on elements that might have different computed values based on visited status. This capability directly violates user privacy expectations and can be used to build detailed profiles of browsing behavior without explicit user consent. The vulnerability particularly affects users who rely on these applications for sensitive activities where maintaining browsing privacy is crucial.
Security professionals should note that this vulnerability aligns with CWE-200, which addresses "Information Exposure," and demonstrates how seemingly benign API implementations can become attack vectors when proper input validation and output sanitization are absent. The attack pattern follows typical reconnaissance techniques described in the MITRE ATT&CK framework under the Information Gathering phase, where adversaries seek to understand system state and user behavior through indirect means. Organizations should prioritize updating affected applications to versions that properly sanitize the getComputedStyle method outputs and implement comprehensive monitoring for suspicious API usage patterns that might indicate exploitation attempts.
The remediation approach requires updating to patched versions of Firefox, Thunderbird, and SeaMonkey where the getComputedStyle method has been properly constrained to return only valid computed style values. Additionally, security teams should implement application-level monitoring to detect unusual patterns of CSS property access that might indicate exploitation attempts. The fix typically involves tightening validation rules on returned values and ensuring that sensitive metadata is not exposed through the JavaScript API. This vulnerability underscores the importance of thorough security testing for all JavaScript APIs and the need for proper input/output validation in web browser implementations to prevent information leakage attacks that can compromise user privacy and security.