This threat concerns malicious Google Chrome browser extensions that inject unauthorized code into web pages or browser processes. Such extensions can manipulate web content, steal sensitive information, perform actions on behalf of the user without consent, or redirect users to malicious sites. The injection of code typically occurs through the extension's ability to execute scripts within the browser context, leveraging permissions granted during installation. These malicious extensions may masquerade as legitimate tools or utilities to deceive users into installing them. Once installed, they can intercept and modify web traffic, capture credentials, or deliver further malware payloads. Although the provided information lacks specific technical details such as the exact injection methods, targeted websites, or persistence mechanisms, the general threat pattern aligns with known abuse of browser extension capabilities. The threat was reported by CIRCL in early 2018, indicating that this is a known but low-severity issue at that time, with no known exploits actively in the wild. The absence of affected versions and patch links suggests this is a generic warning about malicious extensions rather than a vulnerability in Chrome itself.

For European organizations, malicious Chrome extensions pose risks primarily to confidentiality and integrity of data accessed via the browser. Employees using compromised extensions could have their credentials, session cookies, or sensitive corporate data exposed to attackers. This can lead to unauthorized access to corporate systems, data leakage, or further compromise through lateral movement. The impact is heightened in sectors with high reliance on web applications, such as finance, healthcare, and government services. Additionally, organizations with bring-your-own-device (BYOD) policies or less stringent endpoint controls may be more vulnerable. While the threat does not directly affect availability, the indirect consequences of data breaches or unauthorized transactions can be severe. The low severity rating and lack of known exploits suggest the threat is more opportunistic and dependent on user behavior rather than a systemic vulnerability in Chrome.

To mitigate risks from malicious Chrome extensions, European organizations should implement strict extension management policies. This includes whitelisting approved extensions via enterprise policies and disabling installation from untrusted sources. User education is critical to raise awareness about the dangers of installing unknown or suspicious extensions. Regular audits of installed extensions on corporate devices can help detect unauthorized additions. Employing endpoint protection solutions that monitor browser behavior and network traffic can identify suspicious activities related to extensions. Additionally, leveraging Chrome's enterprise features such as force-installing vetted extensions and disabling developer mode can reduce exposure. Organizations should also encourage the use of multi-factor authentication (MFA) to limit the impact of credential theft. Finally, monitoring for unusual account activity and promptly revoking access tokens or sessions when compromise is suspected will help contain potential breaches.