CVE-2017-5393 in Firefox
Summary
by MITRE
The "mozAddonManager" allows for the installation of extensions from the CDN for addons.mozilla.org, a publicly accessible site. This could allow malicious extensions to install additional extensions from the CDN in combination with an XSS attack on Mozilla AMO sites. This vulnerability affects Firefox < 51.
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Analysis
by VulDB Data Team • 08/27/2024
The vulnerability identified as CVE-2017-5393 represents a critical security flaw in Firefox's addon management system that stems from improper trust relationships within the browser's extension installation mechanism. The mozAddonManager component, which handles addon installation and management, was designed to allow extensions to be downloaded from the official Mozilla Add-ons website addons.mozilla.org. However, this design created an unexpected attack vector where malicious actors could exploit the system's trust model to install additional extensions from the same CDN infrastructure that serves legitimate addons. This vulnerability specifically affects Firefox versions prior to 51, where the security boundaries between trusted and untrusted extension sources were insufficiently enforced.
The technical exploitation of this vulnerability relies on the combination of cross-site scripting attacks against Mozilla's own Add-ons website and the browser's trust relationship with the CDN infrastructure. When a user visits a compromised Mozilla AMO page, an XSS payload can execute within the context of the trusted addon domain, allowing attackers to manipulate the mozAddonManager's behavior. The flaw exists because the system does not adequately distinguish between legitimate and malicious extension installations, even when both originate from the same CDN infrastructure. This creates a scenario where an attacker can leverage a single XSS vulnerability on a trusted site to gain persistent access through additional extension installations that bypass normal security checks.
The operational impact of CVE-2017-5393 extends beyond simple extension installation, as it creates a persistent threat vector that can be exploited for long-term compromise of affected Firefox installations. Once a malicious extension is installed through this method, it can maintain persistence on the user's system and potentially exfiltrate data or perform other malicious activities without user interaction. The vulnerability's severity is amplified by the fact that it requires only a single successful XSS attack on a trusted Mozilla domain to establish a foothold, making it particularly dangerous for users who browse Mozilla's official sites regularly. This attack model aligns with the ATT&CK framework's persistence tactics, specifically targeting the installation of malicious software through legitimate system processes.
From a compliance and security standards perspective, this vulnerability relates to CWE-284 which addresses improper access control, and CWE-352 which covers cross-site request forgery vulnerabilities. The flaw demonstrates poor separation of concerns in the browser's security architecture, where the trust boundary between different extension sources was not properly enforced. Organizations and security professionals should note that this vulnerability highlights the importance of maintaining strict security boundaries even within trusted infrastructure, as demonstrated by the fact that extensions from the same CDN can be treated differently based on their source. The mitigation strategy involves upgrading to Firefox 51 or later, where Mozilla implemented additional security checks and improved trust verification mechanisms for addon installations.
The broader implications of this vulnerability extend to how browser vendors approach security in their extension ecosystems, particularly regarding the trust relationships between different components of their security architecture. This flaw demonstrates that even seemingly benign features like CDN-based addon delivery can become attack vectors when proper security boundaries are not maintained. The vulnerability serves as a reminder that security in complex systems requires careful consideration of all potential attack surfaces, including those that might appear to be benign or even beneficial from a user experience perspective. Security practitioners should evaluate their own systems for similar trust relationship issues, particularly where multiple components interact with shared infrastructure and where the distinction between legitimate and malicious behavior might not be adequately enforced.