EUVD-2026-70529

Summary

GET /api/books/{bookID}/notes is an unauthenticated endpoint that accepts a "deleted" query parameter. When the request is ?deleted=true, the service runs the query with Unscoped() (bypassing GORM's soft-delete scope) but keeps the read-authorization clause as "owner_id = ? OR is_public = ?". As a result, any unauthenticated caller can enumerate the metadata of soft-deleted ("trashed") notes belonging to any public book - notes the owner explicitly deleted and expected to be removed from public view.

Affected component (code-verified)

backend/services/notes.go - GetNotesByBookID (lines 72-89):

func (s NotesService) GetNotesByBookID(currentUserID *uuid.UUID, bookID uuid.UUID, deleted bool) ([]db.Note, error) { tx := db.DB if deleted { tx = tx.Unscoped() // <-- bypasses soft-delete scope } tx = tx. Preload("Book"). Joins("JOIN books ON books.id = notes.book_id"). Where( db.DB.Where("books.id = ?", bookID), db.DB.Where("owner_id = ? OR is_public = ?", currentUserID, true), // <-- is_public still honored for trash ) if deleted { tx = tx.Where("notes.deleted_at IS NOT NULL") } var notes []db.Note return notes, dbErrorToServiceError(tx.Find(&notes).Error) }

Route registration confirms the endpoint has no AuthRequiredMiddleware (backend/handlers/notes.go:37), and the deleted flag is attacker-controlled (backend/handlers/notes.go:86 - Deleted bool with query:"deleted").

Proof of concept

1. A victim owns a public book (is_public = true), creates a note, then soft-deletes it (moves it to trash). The note still exists in the DB with

deleted_at set.

1. An unauthenticated attacker who knows (or enumerates) the book UUID requests: GET /api/books/<bookID>/notes?deleted=true
2. The response lists the soft-deleted note(s) - id, title, slug, timestamps - even though the attacker is not authenticated and the owner

intended the note to be deleted.

Impact

Exposure of soft-deleted note metadata (title, slug, timestamps) of public books to unauthenticated actors. The note body is not exposed - the content endpoint (GetNoteContent) does not use Unscoped(), so its count query returns 0 for soft-deleted notes and yields 404. Impact is therefore limited to metadata disclosure and the bypass of the intended "delete" semantics on public books.

Remediation

Restrict trash (soft-deleted) listings to the book owner only - never honor the is_public branch when deleted=true:

func (s NotesService) GetNotesByBookID(currentUserID *uuid.UUID, bookID uuid.UUID, deleted bool) ([]db.Note, error) { tx := db.DB if deleted { tx = tx.Unscoped() } + // Soft-deleted ("trash") notes must only ever be listed to the book owner. + authz := db.DB.Where("owner_id = ? OR is_public = ?", currentUserID, true) + if deleted { + authz = db.DB.Where("owner_id = ?", currentUserID) + } tx = tx. Preload("Book"). Joins("JOIN books ON books.id = notes.book_id"). Where( db.DB.Where("books.id = ?", bookID),

• db.DB.Where("owner_id = ? OR is_public = ?", currentUserID, true),

+ authz, ) if deleted { tx = tx.Where("notes.deleted_at IS NOT NULL") } var notes []db.Note return notes, dbErrorToServiceError(tx.Find(&notes).Error) }

With this change, when currentUserID is nil (unauthenticated) and deleted=true, the clause becomes owner_id = NULL, which matches nothing - so trash is never exposed to anonymous callers.

Coordinated disclosure / CVE request

We have reported this privately and are happy to assist with any further validation or testing you need. If you agree this qualifies as a security vulnerability, we would be grateful if you could request a CVE ID for it - GitHub lets maintainers request a CVE directly from this advisory page once it is accepted. Thank you for your time and for maintaining note-mark.

References

• CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
• CWE-285: Improper Authorization
• Prior note-mark authorization fix (CVE-2026-40265) established that read paths must scope by owner_id OR is_public; this report covers the trash

path that the scope did not fully cover.

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