Also if you set cookies in your app with the scope of your main domain with the hope that they are visible to all of the subdomains you provide for your custome

Also if you set cookies in your app with the scope of your main domain with the hope that they are visible to all of the subdomains you provide for your customers, these cookies are also accessible by 3rd party services that use your subdomains. So if you run acme.com and give our subdomain to your clients you could end up with client1.acme.com and client2.acme.com. You decide to store cookies on acme.com. The. You decide that you will use SupportCorp’s helpdesk software and host it on support.acme.com. If a logged in user goes to support.acme.com they will send their cookies to SupportCorp’s servers. This might include session ids and other highly sensitive info.