Lab 108 — CostPilot — IDOR via Deprecated v1 API Endpoint

hackadvisor

Task: expense management platform migrated from v1 (numeric IDs) to v2 (UUID-based) API, with deprecated v1 endpoints still partially active. Solution: discover API versioning via X-API-Version header, enumerate /api/v1/expenses/{id} with sequential numeric IDs to access another user's confidential expenses containing the flag.