CVE-2010-0648 in Firefox
Summary
by MITRE
Mozilla Firefox, possibly before 3.6, allows remote attackers to discover a redirect's target URL, for the session of a specific user of a web site, by placing the site's URL in the HREF attribute of a stylesheet LINK element, and then reading the document.styleSheets[0].href property value, related to an IFRAME element.
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Analysis
by VulDB Data Team • 04/30/2026
This vulnerability exists in mozilla firefox versions prior to 3.6 and represents a significant information disclosure flaw that exploits the browser's handling of stylesheet loading and url resolution. The vulnerability stems from the improper isolation of stylesheet resources within the browser's security model, allowing malicious actors to extract sensitive redirect target urls from web applications. The technical implementation involves placing a website's url within the href attribute of a stylesheet link element, which then enables attackers to access the document.styleSheets[0].href property value through javascript execution. This particular flaw demonstrates a failure in firefox's cross-origin resource handling and demonstrates how seemingly innocuous stylesheet processing can become a vector for information leakage.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive redirect targets that may include authentication tokens, session identifiers, or other confidential data passed through url parameters. Attackers can leverage this technique to perform targeted information gathering against specific user sessions, potentially leading to session hijacking or further exploitation of web applications that rely on redirect mechanisms. The vulnerability particularly affects web applications that use redirect patterns for authentication flows or access control, where the target url of a redirect may contain sensitive information that should remain confidential. This issue aligns with CWE-200, which addresses improper information disclosure, and demonstrates how browser security boundaries can be circumvented through creative exploitation of legitimate web features.
The exploitation technique leverages the fact that firefox maintains a reference to the stylesheet's href property even when the stylesheet has not yet been loaded or when the loading process fails, providing attackers with access to the original url that would normally be hidden during the redirect process. This behavior creates a timing attack vector where the attacker can observe the url resolution process through javascript and extract information that should remain private. The vulnerability also relates to ATT&CK technique T1071.004, which covers application layer protocol: web protocols, as it exploits the http protocol handling within the browser's rendering engine. The flaw essentially bypasses firefox's normal security mechanisms that should prevent cross-site information leakage through legitimate web resource loading patterns.
Mitigation strategies for this vulnerability involve updating firefox to version 3.6 or later, where the browser's stylesheet handling has been modified to prevent exposure of redirect target urls through the document.styleSheets interface. Additionally, web application developers should implement proper security headers, including Content Security Policy directives that limit stylesheet loading from untrusted origins, and should avoid relying on redirect mechanisms that expose sensitive information in url parameters. Network security controls such as web application firewalls can also provide additional protection by monitoring for suspicious stylesheet loading patterns. The vulnerability highlights the importance of comprehensive browser security testing and demonstrates how seemingly benign features like stylesheet loading can become attack vectors when not properly isolated from sensitive information processing. Organizations should ensure that their firefox installations are kept up to date with the latest security patches and that they implement appropriate monitoring for suspicious browser behavior that may indicate exploitation attempts.