Unenrolled Users Able to Take Curriculum

I have created a training curriculum in the Shared Training folder on Adobe Connect Central. It is not in the training catalogue and self-enrollment is not enabled.

I have had 2 users tell me they have completed the training, even though they were never enrolled. I assumed that someone must have shared the link with them, and confirmed this by giving the link to an unenrolled coworker who said he could take the training. 

How I can prevent this? Users should only be allowed to take the training if enrolled by someone on my team.