CVE-2018-5132 in Firefox
Summary
by MITRE
The Find API for WebExtensions can search some privileged pages, such as "about:debugging", if these pages are open in a tab. This could allow a malicious WebExtension to search for otherwise protected data if a user has it open. This vulnerability affects Firefox < 59.
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Analysis
by VulDB Data Team • 02/05/2021
The vulnerability identified as CVE-2018-5132 represents a significant security flaw in the Firefox browser's WebExtensions API implementation that exposes privileged content to malicious extensions. This issue specifically impacts Firefox versions prior to 59, where the Find API for WebExtensions was designed to search through web content but inadvertently permitted access to sensitive privileged pages that should remain protected from extension interference. The vulnerability stems from insufficient access controls within the browser's extension framework, allowing extensions to query content that would normally be restricted to prevent unauthorized access to system information and debugging interfaces.
The technical flaw manifests through the improper handling of privileged page access within Firefox's WebExtensions architecture. When users have tabs open containing privileged pages such as "about:debugging", "about:config", or similar system interfaces, the Find API enables malicious extensions to perform searches across these pages without proper authorization. This occurs because the API lacks adequate sandboxing mechanisms to distinguish between regular web content and sensitive system interfaces that should remain isolated from extension access. The vulnerability is classified under CWE-284 Access Control, specifically involving insufficient access control mechanisms that allow unauthorized access to privileged resources.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential attack vectors for malicious actors to gather sensitive system information and debugging data. Attackers could leverage this flaw to extract configuration details, debugging information, or other privileged data that might reveal system vulnerabilities or user activities. This capability significantly increases the risk of further exploitation, as the gathered information could be used to craft more sophisticated attacks or to identify additional system weaknesses. The vulnerability directly aligns with ATT&CK technique T1112, which involves the use of system information discovery to gather data about the operating environment and system configuration.
The security implications are particularly concerning given that users might have privileged pages open in tabs without realizing the potential risks to their browsing environment. The vulnerability demonstrates a fundamental flaw in Firefox's privilege separation model, where the boundary between user-facing content and system-privileged interfaces becomes blurred through the extension API. This creates a persistent threat vector that remains active as long as users maintain open tabs containing privileged content, making it particularly dangerous in environments where users frequently access debugging or configuration interfaces. Organizations should consider this vulnerability as part of a broader security assessment that includes user behavior analysis and extension management policies to prevent exploitation.
Mitigation strategies for CVE-2018-5132 primarily focus on upgrading to Firefox version 59 or later, where the vulnerability has been addressed through enhanced access controls and stricter privilege boundaries within the WebExtensions API. System administrators should implement comprehensive extension management policies that restrict the installation and capabilities of third-party extensions, particularly those with access to search or content manipulation functions. Additionally, users should be educated about the risks of keeping privileged pages open in browser tabs and encouraged to close such tabs when not actively needed. The fix implemented by Mozilla involved strengthening the API's access control mechanisms to ensure that privileged pages are properly isolated from extension queries, thereby preventing unauthorized data access while maintaining legitimate extension functionality.