By default vidoes are not domain restricted, so anyone can embed your video onto any page on the internet if they have embed code.
Restrict where your video can be embedded
Go to settings page.
From the sidebar click on Embed videos
Add your website’s subdomain (subdomain.mysite.com) in the text field that appears; be sure to click save to add it. You can specify and manage up to 50 domains where your video can be embedded.
Wildcard characters are not supported.