Supabase is an open source Firebase alternative. Start your project with a Postgres database, Authentication, instant APIs, Edge Functions, Realtime subscriptions, and Storage.

Supabase

You should use it to store mostly pictures/ documents. If you need, you can use Virus Total (or a similar API) to verify the document. But it is not something scanned by default. 

https://developers.virustotal.com/reference/overview

I'm short on time and experience, but I guess this can open up a suggestion - for you to add these features in built

Services like AWS and Google Cloud provide it.

Feel free to suggest it here:

https://github.com/supabase/supabase/discussions/categories/ideas