CVE-2004-2260 in Web Browser
Summary
by MITRE
Opera Browser 7.23, and other versions before 7.50, updates the address bar as soon as the user clicks a link, which allows remote attackers to redirect to other sites via the onUnload attribute.
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Analysis
by VulDB Data Team • 03/09/2021
The vulnerability described in CVE-2004-2260 represents a critical security flaw in Opera Browser versions prior to 7.50 that fundamentally compromises user navigation integrity and trust. This issue stems from the browser's improper handling of address bar updates during page transitions, creating an exploitable condition that allows remote attackers to manipulate user sessions through carefully crafted web content. The flaw specifically manifests when users click on links that contain malicious onUnload attributes, enabling attackers to redirect users to unintended destinations without their knowledge or consent.
The technical implementation of this vulnerability involves the browser's address bar update mechanism being triggered prematurely during the page unload process. When a user clicks a link containing an onUnload attribute, the browser updates the address bar before the page has fully transitioned, creating a window where malicious code can execute and redirect the user to a different website. This behavior violates fundamental security principles of browser isolation and user intent preservation, as the browser fails to maintain proper state boundaries between different web pages. The vulnerability operates at the intersection of client-side scripting execution and browser navigation protocols, exploiting a race condition between user interaction and page rendering processes.
From an operational impact perspective, this vulnerability creates significant risks for user security and privacy across multiple threat vectors. Attackers can leverage this flaw to implement sophisticated phishing campaigns, where users are redirected to malicious sites that appear legitimate due to the address bar update timing. The vulnerability also enables session hijacking scenarios where users might be unknowingly redirected to attacker-controlled domains while believing they are navigating within their original session. This type of attack directly violates the principle of least privilege and user autonomy, as it manipulates browser behavior in ways that bypass standard security controls and user expectations. The impact extends beyond simple redirection to encompass potential credential theft, malware delivery, and data exfiltration opportunities.
Mitigation strategies for this vulnerability require immediate browser version updates to Opera 7.50 or later, which addressed the underlying address bar update logic. Organizations should implement comprehensive browser security policies that enforce regular updates and monitor for vulnerable browser versions in their environments. Network administrators should consider implementing web content filtering solutions that can detect and block suspicious onUnload attribute usage, though this represents a reactive approach rather than a fundamental fix. The vulnerability aligns with CWE-601 URL Redirection to Untrusted Site and ATT&CK technique T1189 for exploitation through web browsers. Security teams should also conduct user awareness training to educate individuals about suspicious browser behavior and the importance of verifying address bar integrity during navigation. This vulnerability demonstrates the critical importance of maintaining up-to-date browser software and highlights how seemingly minor implementation flaws can create significant security risks that affect millions of users.