Locking down who can open a page is the part everyone thinks about. You put it behind auth, you invite people by email, you set an expiry. Done.
Then the page loads and starts making requests you never looked at.
This is the part I got wrong for a while, and I only really got pushed on it last week when someone on Indie Hackers said, roughly: private mode is only real if auth gates every asset before any bytes leave the server, and generated HTML can still leak through embedded data, public JSON, images, and third party scripts. They were right, and the second half of that sentence is the interesting half.
Why AI-generated pages make this sharper
When you write a page by hand, you know what is in it. When you ask a model for "a dashboard for this data" you get back something that works, and somewhere in it there may be a font from a CDN, an analytics snippet it added out of habit, a chart library pulled from unpkg, an image hotlinked from wherever the model saw one. None of that is malicious. It is just the model producing the most common shape of the thing you asked for.
