Extensions installation must be blocklisted by default.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-235754	SRG-APP-000141	EDGE-00-000041	SV-235754r960963_rule	2024-09-13	2

Description
List specific extensions that users cannot install in Microsoft Edge. When this policy is deployed, any extensions on this list that were previously installed will be disabled, and the user will not be able to enable them. If an item is removed from the list of blocked extensions, the extension is automatically reenabled anywhere it was previously installed. Use "*" to block all extensions that are not explicitly listed in the allow list. If this policy is not configured, users can install any extension in Microsoft Edge.

Description

List specific extensions that users cannot install in Microsoft Edge. When this policy is deployed, any extensions on this list that were previously installed will be disabled, and the user will not be able to enable them. If an item is removed from the list of blocked extensions, the extension is automatically reenabled anywhere it was previously installed. Use "*" to block all extensions that are not explicitly listed in the allow list. If this policy is not configured, users can install any extension in Microsoft Edge.

ℹ️ Check
The policy value for "Computer Configuration/Administrative Templates/Microsoft Edge/Extensions/Control which extensions cannot be installed" must be set to "Enabled". Use the Windows Registry Editor to navigate to the following key: HKLM\SOFTWARE\Policies\Microsoft\Edge\ExtensionInstallBlocklist\1 If the value for "1" is not set to "REG_SZ = *", this is a finding.

✔️ Fix
Set the policy value for "Computer Configuration/Administrative Templates/Microsoft Edge/Extensions/Control which extensions cannot be installed" to "Enabled". A list of blocklisted extensions may then be specified.