CVE-2017-7830 in Firefox
Summary
by MITRE
The Resource Timing API incorrectly revealed navigations in cross-origin iframes. This is a same-origin policy violation and could allow for data theft of URLs loaded by users. This vulnerability affects Firefox < 57, Firefox ESR < 52.5, and Thunderbird < 52.5.
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Analysis
by VulDB Data Team • 11/26/2025
The Resource Timing API in web browsers provides detailed timing information about resource loading operations, including network requests and page navigation events. This API is designed to help developers optimize web applications by exposing performance metrics such as DNS lookup times, connection times, and request/response durations. However, the vulnerability described in CVE-2017-7830 represents a critical breach in the browser's security model that undermines fundamental web security principles. The flaw specifically affects how the API handles cross-origin iframe navigation events, creating an unintended information disclosure channel that violates core web security concepts.
The technical implementation of this vulnerability stems from improper enforcement of same-origin policy restrictions within the Resource Timing API. When a web page contains cross-origin iframes, the browser should typically restrict access to timing information about resources loaded in those iframes to prevent information leakage. However, the flaw allowed the Resource Timing API to expose navigation timing data for cross-origin iframes, effectively bypassing the same-origin policy that normally protects users from malicious scripts accessing sensitive information from other domains. This issue manifests particularly in browsers where the API was not properly validating the origin of iframe content before exposing timing information, creating a pathway for attackers to gather information about user navigation patterns and potentially sensitive URLs.
The operational impact of this vulnerability extends beyond simple information disclosure, creating significant risks for user privacy and data protection. Attackers could exploit this flaw to reconstruct user browsing behavior by monitoring navigation timing data from cross-origin iframes, potentially identifying which websites users visit and when they access them. This information could be combined with other reconnaissance techniques to build detailed profiles of user activities, track user movements across the web, and even identify sensitive websites or services that users access. The vulnerability particularly affects users of older browser versions where the security patch had not yet been implemented, making them susceptible to attacks that could compromise their browsing privacy and potentially expose confidential information.
Organizations and security teams should prioritize immediate remediation of this vulnerability by updating affected browser versions to the patched releases. Mozilla's security advisories for Firefox 57 and Thunderbird 52.5 included the necessary fixes that properly enforce same-origin policy restrictions within the Resource Timing API. The mitigation strategy involves not only updating browser software but also implementing additional monitoring to detect potential exploitation attempts. Security professionals should consider this vulnerability as part of broader web application security assessments and ensure that web applications properly validate and sanitize timing information when processing data from potentially untrusted sources. This vulnerability aligns with CWE-200 (Information Exposure) and represents a specific implementation weakness in browser security controls that could enable advanced persistent threats to gather intelligence about user activities and website access patterns.
The broader implications of this vulnerability highlight the critical importance of proper API security implementation in web browsers. The Resource Timing API should have enforced strict origin validation before exposing timing information, preventing cross-origin data leakage while maintaining legitimate performance monitoring capabilities. This flaw demonstrates how subtle implementation errors in security controls can create significant risks for user privacy and data protection. Security professionals should also consider the ATT&CK framework's techniques for reconnaissance and credential access when evaluating the potential impact of similar vulnerabilities. The vulnerability serves as a reminder that even well-established browser APIs require continuous security review and testing to prevent unintended information disclosure that could compromise user privacy and system security.