Information
If you select 'Only in the same organization', users may still be able to chat with external users if they are added to channels or group chats with external users. If this option is required to be enabled, then choose 'Only in the same organization and specified domains' and specify the domains for better security.
Rationale:
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
Go into the Zoom Admin Dashboard on the zoom website. Account Management -> IM Management -> IM Settings -> Security -> Allow users to chat with others, and ensure it is disabled.