TREK is a collaborative travel planner. From 3.0.0 until 3.1.0, the GET /api/journeys/:id/share-link route in server/src/routes/journey.ts returns the result of getJourneyShareLink() from server/src/services/journeyShareService.ts without checking whether the authenticated requester can access the journey. Any ordinary authenticated user can enumerate sequential journey IDs and retrieve tokens from journey_share_tokens for another user's journey. The token grants unauthenticated access through G