I'm planning a tool that will allow users to publish collections of their writing for publish consumption.
Any modification of content or account settings will be done through a secure management / admin server
When users choose to publish a collection, they will be allowed to choose a subdomain from a different TLD, reserved specifically for published content:
Since the published collections are on their own subdomain of a TLD that's completely separate from the management server, I think that users would be protected from XSS attacks.
What other risks, if any, would I be exposing readers to by allowing custom JS execution?