I have a domain, let's call it `www.mydomain.com` where I have a portal with an active community of users.

In this portal users cooperate in a wiki way to build some "kind of software".
These software applications can then be run by accessing `"public.mydomain.com/softwarename"`

I then want to let my users run these applications from their own subdomains. I know I can do that by automatically modifying the.htaccess file. This is not a problem.

I want to let these users create dns aliases to let them access one specific subdomain. So if a user `"pippo"` that owns `"www.pippo.com"` wants to run software HelloWorld from his own subdomains he has to:

1. Register to my site
2. Create his own subdomain on his own site, run.pippo.com
3. From his DNS control panel, he creates a CNAME record `"run.pippo.com"` pointing to `"public.mydomain.com"`
4. He types in a browser `http://run.pippo.com/HelloWorld`

When the software(that is physically run on my server) is called, first it checks that the originating domain is a trusted one. I don't do any other kind of check that restricts software execution.

From a SEO perspective, I care about Google indexing of `www.mydomain.com` but I don't care about indexing of `public.mydomain.com`

What are the possible security implications of doing this for my site?

Do you know some existing website implementing a domain configuration like this one?