CVE-2014-1504 in Firefox
Summary
by MITRE
The session-restore feature in Mozilla Firefox before 28.0 and SeaMonkey before 2.25 does not consider the Content Security Policy of a data: URL, which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via a crafted document that is accessed after a browser restart.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 05/08/2026
The vulnerability described in CVE-2014-1504 resides in the session-restore functionality of Mozilla Firefox versions prior to 28.0 and SeaMonkey versions prior to 2.25. This flaw represents a critical security oversight that directly impacts how browsers handle persistent session data across restarts. The session-restore feature is designed to maintain user navigation state and session information, including open tabs and their content, to provide a seamless browsing experience upon browser restart. However, the implementation contained a fundamental flaw in its security model that created an exploitable gap in the browser's protection mechanisms.
The technical root cause of this vulnerability stems from the improper handling of Content Security Policy (CSP) enforcement during the session restoration process. When Firefox restores sessions, it reconstructs the browser state including the content of previously loaded pages. The vulnerability occurs specifically when dealing with data: URLs, which are special URLs that contain the actual data inline rather than referencing an external resource. During session restoration, the browser fails to properly validate or enforce the CSP directives that were originally applied to the data: URL content, effectively bypassing security controls that should have prevented malicious script execution. This failure creates an environment where attackers can craft malicious documents that appear benign when initially loaded but become dangerous upon session restoration.
The operational impact of this vulnerability is significant and directly enables cross-site scripting attacks that would otherwise be prevented by proper CSP enforcement. Attackers can exploit this weakness by creating malicious documents that are loaded in a data: URL context and then saved in the browser's session. When users restart their browsers and the session is restored, the malicious content executes with the privileges and security context of the original page, potentially allowing attackers to steal session cookies, perform unauthorized actions, or exfiltrate sensitive information. The vulnerability is particularly dangerous because it leverages the legitimate session-restore functionality to bypass security controls, making the attack vector more subtle and harder to detect than traditional XSS techniques. This type of vulnerability falls under CWE-1004 which specifically addresses insecure coding practices related to security controls and enforcement mechanisms.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, particularly in the context of initial access and execution phases. The attack pattern demonstrates how attackers can leverage browser features designed for user convenience to create security breaches, representing a sophisticated approach to bypassing traditional security controls. This vulnerability also highlights the importance of maintaining security posture across all browser components, including seemingly benign features like session management. Organizations should consider this vulnerability as part of broader browser security hygiene practices, recognizing that even features designed to improve user experience can introduce security risks if not properly implemented with security controls in mind. The remediation requires updating to versions where the session-restore functionality properly enforces CSP policies for all restored content, including data: URLs, ensuring that security contexts are maintained consistently across browser sessions.