CVE-2025-9866: 
vulnerability analysis and mitigation

CVE-2025-9866 is a security vulnerability discovered in Google Chrome's Extensions implementation. The vulnerability affects versions prior to 140.0.7339.80 and was disclosed on September 3, 2025. The issue allows remote attackers to bypass content security policy through a crafted HTML page (NVD).

The vulnerability has been assigned a CVSS v3.1 Base Score of 8.8 (HIGH) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. It is classified as a Protection Mechanism Failure (CWE-693) that specifically affects the Extensions component of Google Chrome. The vulnerability requires user interaction and can be exploited remotely without requiring privileges (NVD).

The vulnerability's high CVSS score indicates significant potential impact, with possible consequences affecting confidentiality, integrity, and availability of the system. The ability to bypass content security policy could potentially allow attackers to execute unauthorized code or access restricted content (NVD).

Google has released version 140.0.7339.80 of Chrome to address this vulnerability. Users are advised to update their Chrome browsers to this version or later. The fix has been incorporated into the stable channel update for Windows, Mac, and Linux platforms (Chrome Release).