TREK is a collaborative travel planner. Prior to 3.3.0, the DELETE /api/trips/:tripId/collab/notes/:noteId/files/:fileId endpoint authorizes an authenticated user against the attacker-controlled tripId but deleteNoteFile in server/src/services/collabService.ts resolves the target only by note and file identifiers without requiring the file to belong to that trip. A user with edit access to any trip can submit identifiers belonging to another user's trip and permanently delete that note-file attachment. Sequential identifiers make broad targeting practical, while attachment read operations remain trip-scoped and are not affected. This issue is fixed in version 3.3.0.