Hello!
Key moment: To use Browser extensions assessment you'll require Microsoft Defender Vulnerability Management Standalone or if you're already a Microsoft Defender for Endpoint Plan 2 customer, the Defender Vulnerability Management Add-on (this is a separate product). If you have Defender for Server Plan 2, there are Defender Vulnerability Management add-on features (in particular Browser extensions). So only on servers that exist in subscription with Defender for Server Plan 2 Browser extensions feature will work. No additional actions need to be taken, Browser extensions information will be updated regularly in your Microsoft Defender portal.
You can see this message in Vulnerability Management => Inventories:
You can read more via this article.
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