CVE-2008-3836 in Firefox
Summary
by MITRE
feedWriter in Mozilla Firefox before 2.0.0.17 allows remote attackers to execute scripts with chrome privileges via vectors related to feed preview and the (1) elem.doCommand, (2) elem.dispatchEvent, (3) _setTitleText, (4) _setTitleImage, and (5) _initSubscriptionUI functions.
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Analysis
by VulDB Data Team • 08/17/2019
The vulnerability identified as CVE-2008-3836 represents a critical cross-site scripting flaw in Mozilla Firefox versions prior to 2.0.0.17, specifically within the feedWriter component that handles RSS and Atom feed processing. This vulnerability exploits the browser's feed preview functionality, creating a pathway for remote attackers to execute malicious scripts with elevated chrome privileges that typically should be restricted to browser internals. The flaw resides in how Firefox processes feed content through the feedWriter module, which is responsible for displaying feed previews to users. Attackers can leverage this vulnerability by crafting malicious feed content that triggers specific JavaScript execution paths when the browser attempts to render feed elements.
The technical exploitation occurs through five distinct function vectors that demonstrate a sophisticated attack surface within Firefox's feed processing architecture. The elem.doCommand function allows manipulation of command execution within the feed context, while elem.dispatchEvent enables attackers to trigger event handlers that can execute arbitrary code. The _setTitleText and _setTitleImage functions provide additional attack vectors for manipulating feed display elements, and _initSubscriptionUI offers a pathway for initializing malicious subscription interfaces. These functions collectively represent a complex attack surface that bypasses normal security boundaries, allowing attackers to execute code with chrome privileges that typically have access to sensitive browser internals and user data. This vulnerability specifically maps to CWE-79 Cross-site Scripting and CWE-94 Code Injection, demonstrating how feed processing can become a vector for privilege escalation.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to gain access to sensitive browser functionality and user data through the chrome privilege escalation. An attacker could potentially read user cookies, access local files, modify browser settings, or even redirect users to malicious websites without their knowledge. The feed preview functionality is particularly dangerous because it is often used to display content from untrusted sources, making it a natural target for exploitation. Users who have not updated their browsers to version 2.0.0.17 or later are at risk of having their systems compromised through malicious feed content, potentially leading to full system compromise. This vulnerability aligns with ATT&CK technique T1059 Command and Scripting Interpreter and T1071.004 Application Layer Protocol Web Protocols, demonstrating how feed processing can be weaponized for malicious purposes.
Mitigation strategies for CVE-2008-3836 require immediate browser updates to version 2.0.0.17 or later, which contain patches addressing the feedWriter privilege escalation issues. Organizations should implement feed filtering policies and disable automatic feed preview rendering where possible, particularly in environments where users may encounter untrusted content. Security administrators should also consider implementing content filtering solutions that can detect and block malicious feed content before it reaches user browsers. The vulnerability highlights the importance of keeping browser software updated, as it demonstrates how seemingly benign features like feed preview can become attack vectors when not properly secured. Additionally, user education regarding the risks of clicking on untrusted feed links and the importance of browser updates remains crucial in defending against such exploits. The patch for this vulnerability specifically addresses the privilege escalation mechanisms in the feedWriter component and implements stricter input validation for feed content processing.