CVE-2008-4696 in Web Browser
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Opera.dll in Opera before 9.61 allows remote attackers to inject arbitrary web script or HTML via the anchor identifier (aka the "optional fragment"), which is not properly escaped before storage in the History Search database (aka md.dat).
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Analysis
by VulDB Data Team • 04/23/2025
This cross-site scripting vulnerability exists in Opera web browser versions prior to 9.61 where the Opera.dll component fails to properly sanitize anchor identifiers or fragment parameters in web URLs. The flaw occurs when users navigate to web pages containing malicious fragment identifiers that are subsequently stored in the browser's History Search database file named md.dat. The vulnerability specifically targets the handling of optional fragment components in URLs, which are typically used to specify particular sections within a webpage or to pass parameters to client-side scripts. When these fragment identifiers contain malicious script code, the improper escaping allows the code to persist in the local history database and potentially execute when the user revisits the page or interacts with the history functionality.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the browser's history management system. Fragment identifiers in URLs follow the format www.example.com/page.html#fragment where the fragment part after the hash symbol is intended to be processed by client-side applications or used for internal page navigation. However, Opera's Opera.dll component does not adequately escape these fragment values before storing them in the md.dat database file, creating a persistent storage vulnerability. This allows attackers to craft malicious URLs with embedded script payloads in the fragment identifier that survive the browser's normal processing and storage mechanisms.
The operational impact of this vulnerability extends beyond simple script injection as it provides attackers with a method to establish persistent malicious presence within a user's browser history database. When users revisit pages containing malicious fragments, or when the browser's history search functionality processes these stored values, the injected scripts can execute in the context of the user's browsing session. This creates opportunities for session hijacking, credential theft, or redirection to malicious sites. The vulnerability is particularly dangerous because it leverages the browser's legitimate history functionality to maintain persistence, making detection more difficult for both users and security tools that might not immediately recognize malicious code embedded in the history database.
This vulnerability maps to CWE-79 Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly escape user-controllable input in web applications. The attack pattern aligns with ATT&CK technique T1059.001 Command and Scripting Interpreter: PowerShell, as it enables attackers to execute arbitrary code through the browser's history management system. The persistence mechanism through the md.dat database file represents a form of T1078 Valid Accounts exploitation where malicious code can be stored and executed without requiring additional user interaction or network access. Organizations should implement immediate patching of affected Opera versions and consider monitoring for suspicious fragment identifiers in browser history databases. Additionally, browser security policies should be updated to enforce proper input sanitization for all URL components, particularly fragment identifiers that are often overlooked in security validation processes.
The vulnerability demonstrates how seemingly benign browser features can become attack vectors when proper input validation is absent. The History Search database functionality, designed to help users quickly find previously visited pages, becomes a persistent storage mechanism for malicious content when fragment identifiers are not properly escaped. This creates a unique attack surface that combines both client-side script execution and local data persistence, making it particularly challenging to detect and remediate. Security professionals should be aware that vulnerabilities of this nature often require comprehensive browser updates rather than simple configuration changes, as they typically involve core browser components that handle URL processing and storage. The remediation process must ensure that all fragment identifiers are properly encoded and validated before any storage operations occur, preventing malicious code from being embedded in the browser's local database files.