In case anyone else needs this, I thought I would post about. We just installed Directory Server 11 Update 5 and ran into a problem with iframes that were embedded in some of our Forms processes. The servers are on sub.domain1.com, and domain2.local. We use aliases for these servers and because of this the Forms processes were showing an error message that the LFDSSTS server refused to connect.
I was able to add a single domain to the LFDSSTS page in the "Allowed IFrame Hosts" field and it resolved the issue for one of the domains. I then tried to add a second domain and finally figured out, after some trial and error, the format that it needs to be in.
If you are entering more than one domain in the "Allowed IFrame Hosts" field in the LFDSSTS, you separate them with a space. Using my example above it would be "subdomain.domain1.com domain2.local".
I hope this helps someone else.