CVE-2006-6507 in Firefox
Summary
by MITRE
Mozilla Firefox 2.0 before 2.0.0.1 allows remote attackers to bypass Cross-Site Scripting (XSS) protection via vectors related to a Function.prototype regression error.
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability identified as CVE-2006-6507 represents a critical security flaw in Mozilla Firefox version 2.0.0.0 and earlier, which enabled remote attackers to circumvent the browser's built-in cross-site scripting protection mechanisms. This issue stems from a regression error within the Function.prototype object implementation, which is a fundamental component of javascript execution in web browsers. The flaw specifically affects the browser's ability to properly sanitize and validate javascript code, creating a pathway for malicious actors to execute unauthorized scripts in the context of trusted websites. Such bypass capabilities directly undermine the core security model that browsers employ to protect users from malicious code injection attacks.
The technical root cause of this vulnerability lies in how Firefox handled javascript function prototypes during the processing of web content. When a javascript function prototype was manipulated or accessed in specific ways, the browser's security checks failed to properly validate the code's origin and intent. This regression error essentially created a loophole in the browser's content security policies, allowing attackers to craft malicious javascript payloads that would be executed without triggering the expected XSS protection mechanisms. The vulnerability exploited the inherent trust model of web browsers where javascript execution is typically restricted based on domain boundaries and security contexts. According to CWE-79, this represents a classic cross-site scripting weakness where insufficient input validation allows malicious scripts to be injected into web applications.
The operational impact of this vulnerability extends far beyond simple script execution, as it fundamentally compromises user security across the entire firefox user base. Attackers could leverage this flaw to steal session cookies, perform unauthorized transactions, redirect users to malicious sites, or extract sensitive information from authenticated sessions. The vulnerability was particularly dangerous because it affected the browser's core protection mechanisms rather than just specific web applications, meaning that any website visited by an affected firefox user could potentially be exploited. This type of attack vector aligns with ATT&CK technique T1059.007 for scripting and T1566 for phishing, as attackers could craft sophisticated social engineering campaigns that would bypass traditional browser security measures.
Mitigation strategies for this vulnerability required immediate patch deployment by Mozilla, with users needing to upgrade to Firefox version 2.0.0.1 or later to restore proper XSS protection. Organizations implementing security policies needed to ensure rapid deployment of the updated browser versions across all user devices. The fix involved correcting the Function.prototype handling code to properly enforce security boundaries and restore the intended validation logic that had been broken by the regression. Additional defensive measures included implementing web application firewalls, content security policies, and enhanced monitoring of suspicious javascript behavior. Security teams needed to conduct thorough vulnerability assessments to identify systems running affected browser versions and prioritize remediation efforts based on risk exposure. The incident highlighted the critical importance of maintaining up-to-date browser security patches and demonstrated how seemingly minor code regressions could have significant security implications for end users.