Moodle Interview Question:

Why are participants being added automatically when a new course is created?

Submitted by: Administrator

If a user is assigned a system role or a role in the course category context then the user has this role in ALL courses in that context. Thus users who are students or teachers at the category level appear as course participants in all courses in that category.

Please check Administration > Users > Permissions > Assign system roles and also the Assign roles link in course categories page and unassign users as necessary.
Submitted by: Administrator