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The book-lookup endpoint returned any book's secret_content to any authenticated caller, keyed only on book_title with no ownership check against the requester. Enforce object-level authorization unconditionally: resolve the requesting user from the validated token's subject, look up the candidate book, and require the book's user_id to match the requester's id before returning its secret. Non-owned or non-existent titles both return a generic 404 so the endpoint doesn't leak which titles exist. Verified locally: logging in as name1 and requesting name2's and admin's books now returns 404 Book not found, while name1's own book still returns 200 with its secret.
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Vulnerability: API1:2019 Broken Object Level Authorization
GET /books/v1/{book_title}looked up the book purely by title (Book.query.filter_by(book_title=...)) and returned itssecret_contentto any authenticated caller, with no check that the caller actually owns that book. Any logged-in user could read any other user's (including admin's) book secrets simply by guessing/enumerating titles.Fix:
api_views/books.pyget_by_title()now resolves the requesting user from the validated token's subject and requires the candidate book'suser_idto match the requester'sidbefore returning the secret. Non-owned and non-existent titles both return a generic 404, so the endpoint no longer distinguishes 'exists but not yours' from 'doesn't exist'.Local verification (WSL, vulnerable=1):
/createdb(name1/pass1 ownsbookTitle3, name2/pass2 ownsbookTitle18, admin ownsbookTitle91).name1, then:GET /books/v1/bookTitle3(own book) → 200 with secret ✔ legitimate access still worksGET /books/v1/bookTitle18(name2's book) → 404 Book not found ✔ exploit blockedGET /books/v1/bookTitle91(admin's book) → 404 Book not found ✔ exploit blocked