Knowledge base gives citations from files that are uploaded in other books

The knowledge base functionality extends beyond individual books, allowing users to obtain citations from files uploaded by themselves or others in different books.

Expected behavior

Knowledge base should be for the specific book only and should give citations only from the files that are uploaded for that specific book.

Current behavior

I can get citations from other books, even books that I don't have access to.

Steps to reproduce

1. Create a book
2. Enable Knowledge base and AI
3. Ask anything to Knowledge base (e.g. in ketty test you can ask about the country of India since there are some chapters uploaded about it)
4. After you get the answer from KB, check the files that are listed in citations.

In the book below, I have just created a new book and haven't uploaded any files in KB for any book. But still, I did get an answer from KB which listed a couple of files as citations.

Screencast from 20.6.24 02:08:26.MD CEST.webm

Environment

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Possible solution

[Not required. Suggest a fix for the bug]