TREK is a collaborative travel planner. Prior to 3.1.0, TREK validates only the initial URL before native redirect following in importGoogleList() and importNaverList() in server/src/services/placeService.ts and resolveGoogleMapsUrl() in server/src/services/mapsService.ts. The affected sinks call checkSsrf() from server/src/utils/ssrfGuard.ts and then use fetch() with redirect: 'follow' instead of the DNS-pinned safeFetch() path, so a public attacker-controlled URL can redirect the server to loopback, RFC 1918, or cloud metadata addresses without revalidation. An authenticated trip member can reach the list-import routes, and any authenticated user can reach /api/maps/resolve-url, allowing blind GET requests to internal services without response-body reflection. This issue is fixed in version 3.1.0.