The default permissions for the recording are set with the person who made the recording as the owner of the video and the Nexus365 users who were on the meeting invite are set as viewers. External or guest meeting participants will not have access to the recording.
Please note that video owners have the ability to open their video up to all Nexus365 users. In the video permissions section, the owner can allow every Nexus365 user the permission to view their video by selecting "Allow everyone in your company to view this video".
Only select this setting if you are sure you want to allow every Nexus365 user access to view your video.
The Microsoft guidance on permissions and privacy provides more information on how to mange video permissions.