Securing Browsing Extensions

Summary:

In December 2024, hackers compromised at least 35 Google Chrome extensions, affecting approximately 2.6 million users. The attack exploited phishing emails sent to developers, masquerading as Google policy violation notices. These emails tricked developers into granting permissions to a malicious OAuth application named

“Privacy Policy Extension.

” Once authorized, the attackers gained control over the extensions, injecting malicious code to steal user data, particularly targeting Facebook credentials and business accounts. Browser extensions can significantly enhance productivity by adding new features to web browsers like Microsoft Edge and Google Chrome. However, they also pose significant security risks, as malicious or compromised extensions can lead to data breaches, malware infections, and unauthorized access to corporate networks. It is crucial for organizations to control, block, or manage browser extensions to minimize security risks, particularly in an enterprise environment. This advisory outlines the steps to block and protect browser extensions for Microsoft Edge and Google Chrome, and it also includes specific guidance on managing extensions using Microsoft Intune.

Risks Associated With Browser Extensions

● Data Exposure: Some extensions can access sensitive data (e.g., browsing history, credentials, and files), potentially exposing confidential information.

● Malicious Extensions: Cybercriminals can create or compromise extensions, making them a vector for malware distribution or data exfiltration.

● Phishing Risks: Extensions may manipulate web content, tricking users into providing sensitive information.

● Performance Degradation: Some poorly coded extensions can slow down browsers or degrade system performance.

Managing Browser Extensions Using Group Policy

A. Microsoft Edge

Using Group Policy (Windows)

1. Open the Group Policy Management Console (GPMC).

2. Navigate to:  Computer Configuration > Administrative Templates > Microsoft Edge > Extensions

3. Set the following policies:

a. Control which extensions are installed silently: Specify allowed extensions by adding their extension IDs.

b. Configure extension management settings: T o block all extensions, set this policy to "*" (deny all).

c. Configure the list of force-installed extensions: If any extension is necessary for business, add the corresponding extension ID here.

‍

B. Google Chrome

Using Group Policy (Windows)

1. Open the Group Policy Editor.

2. Navigate to: Computer Configuration > Administrative Templates > Google > Google Chrome > Extensions

3. Set the following policies:

a. Block external extensions: Set the policy to block all extensions unless specifically allowed by adding the extension IDs.

b. Configure extension install allow list: If certain extensions are necessary, add their extension IDs here.

c. Configure extension install blocklist: Add a wildcard"*" to block all extensions.

_{Managing Browser Extensions Using Microsoft Intune}

Organizations using Microsoft Intune for endpoint management can apply policies to control browser extension installations across all managed devices. This approach is particularly useful for managing large numbers of endpoints efficiently.

Blocking Extensions in Microsoft Edge Using Intune

1. Sign in to Microsoft Endpoint Manager Admin Center.

2. Navigate to: Devices > Configuration profiles > Create profile

3. Choose:

a. Platform: Windows 10 and later.

b. Profile type: Settings catalog.

4. In the Configuration settings, search for Extensions under Microsoft Edge:

a. Allow specific extensions to be installed (User): Specify allowed extension IDs

b. Control which extensions cannot be installed (User): Add a wildcard"*" to block all extensions.

5. Assign this profile to your target groups (specific users or devices).

Blocking Extensions in Google Chrome Using Intune

1. Sign in to Microsoft Endpoint Manager Admin Center.

2. Navigate to: Devices > Configuration profiles > Create profile

3. Choose:

a. Platform: Windows 10 and later.

b. Profile type: Settings catalog.

4. In the Configuration settings, search for Extensions under Google Chrome\Extensions:

a. Configure extension installation allow list (User): Specify allowed extension IDs

b. Configure extension installation blocklist: Add a wildcard"*" to block all extensions.

5. Assign this profile to your target groups (specific users or devices).

Note: These steps are mentioned for user-based controls. Similar configuration steps can be applied for device-based controls.

Best Practices for Managing Browser Extensions

● Audit Extensions Regularly: Regularly audit the extensions installed on users’ browsers to detect unauthorized or risky extensions.

● User Training: Educate users about the risks associated with browser extensions and how to identify malicious ones.

● Implement a Zero-Trust Model: Always assume that extensions can potentially be compromised. Apply the principle of least privilege when granting extension permissions.

● Use Security Solutions: Consider deploying security solutions that can monitor and block malicious browser activities, including suspicious extension behavior.

Conclusion

Controlling browser extensions in Microsoft Edge and Google Chrome is a critical aspect of securing enterprise endpoints. By implementing the steps outlined above, organizations can significantly reduce the risks associated with browser extensions. Whether you manage your endpoints using Group Policy or Microsoft Intune, these controls can help protect your network from potential extension-related threats. By following this advisory, organizations can take proactive steps to mitigate browser extension risks, enhancing their overall cybersecurity posture.

Reference:

https://www.bleepingcomputer.com/news/security/new-details-reveal-how-hackers-hijacked-35-google-chrome-extensions/

https://learn.microsoft.com/en-us/defender-endpoint/manage-profiles-approve-sys-extensions-intune

https://gbhackers.com/malicious-editthiscookie-extension/#google_vignette

Disclaimer

The information contained in this document is meant to provide general guidance and brief information to the intended recipient pertaining to the incident and recommended action. Therefore, this information is provided "as is" without warranties of any kind, express or implied, including accuracy, timeliness, and completeness. Consequently, under NO condition shall CTM360®, its related partners, directors, principals, agents, or employees be liable for any direct, indirect, accidental, special, exemplary, punitive, consequential, or other damages or claims whatsoever including, but not limited to: loss of data, loss in profits/business, network disruption…etc., arising out of or in connection with this advisory.

For more information:

Email: monitor@ctm360.com Tel: (+973) 77 360 360

‍