Might have to introduce moderation to prevent that from happening. Enabling certain npubs to curate submission is my thinking.
Discussion
What’s the login with nostr for? Is it for bookmarks or something similar?
If you give others power to upload, you’ll have to make sure to take down CSAM content. But if you only allow other users to post links to nostr build media, they already take down CSAM. So less maintenance for you. An aggregator would be very good for nostr shitposting.