CVE-2016-8504 in Yandex
Summary
by MITRE
CSRF of synchronization form in Yandex Browser for desktop before version 16.6 could be used by remote attacker to steal saved data in browser profile.
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Analysis
by VulDB Data Team • 05/19/2019
The vulnerability identified as CVE-2016-8504 represents a cross-site request forgery weakness within the Yandex Browser desktop application prior to version 16.6. This security flaw specifically affects the synchronization form functionality that users employ to manage their saved data across devices. The issue stems from the browser's insufficient validation of cross-origin requests, allowing malicious actors to craft specially crafted web pages that can trigger unintended actions within the authenticated browser session.
The technical implementation of this vulnerability exploits the lack of proper anti-CSRF token validation mechanisms within the synchronization form processing. When a user accesses the Yandex Browser's synchronization feature, the application should verify that requests originate from legitimate sources within the same domain. However, the vulnerable implementation failed to enforce this validation, creating an attack surface where remote adversaries could construct malicious HTML content that, when viewed by an authenticated user, would automatically submit synchronization requests without the user's knowledge or consent. This flaw operates under the common weakness pattern classified as CWE-352, which specifically addresses Cross-Site Request Forgery vulnerabilities in web applications and browser implementations.
The operational impact of this vulnerability extends beyond simple data theft, as it allows attackers to potentially manipulate or exfiltrate sensitive user information stored within the browser profile. Attackers could leverage this weakness to steal saved passwords, bookmarks, browsing history, and other personal data that users expect to remain secure within their browser environment. The attack requires minimal user interaction beyond viewing a malicious webpage, making it particularly dangerous in phishing scenarios or when users visit compromised websites. This vulnerability directly relates to the ATT&CK technique T1531, which involves tampering with security tools and defenses, as it undermines the browser's built-in security mechanisms designed to protect user data.
Mitigation strategies for this vulnerability primarily involve updating to Yandex Browser version 16.6 or later, which implements proper CSRF protection mechanisms including anti-CSRF tokens and origin validation. Security researchers recommend that users immediately upgrade their browser installations to address this exposure. Additionally, network administrators should monitor for potential exploitation attempts and consider implementing web application firewalls or content filtering solutions that can detect and block malicious requests targeting synchronization endpoints. The fix typically involves implementing robust token validation, enforcing strict origin checking, and ensuring that all sensitive operations require explicit user confirmation before execution. Organizations should also conduct regular security assessments to identify similar vulnerabilities in other browser applications or web-based services that may be susceptible to the same class of attacks.