Lightdash: Unauthenticated dbt Cloud webhook with path injection leaks API key

Lightdash is an open source business intelligence platform. In affected versions through 0.3213.0, the dbt Cloud webhook `POST /api/v1/projects/{projectUuid}/dbt-cloud/webhook` has no authentication middleware or signature validation. In `packages/backend/src/controllers/projectController.ts`, `testWebhook()` accepts `accountId` and `runId` from a `job.run.completed` request and passes them to `createPreviewWithExplores()` in `packages/backend/src/services/ProjectService/ProjectService.ts`. These unsanitized values are interpolated into the server-side dbt Cloud API URL, which is requested with the victim project's API key in the `Authorization` header. Path traversal through `accountId` changes the requested path on `cloud.getdbt.com` without changing its host, so the credential-bearing request reaches an attacker-influenced path on that fixed host. The advisory claims API-key theft, but the supplied evidence does not establish that the attacker can observe the `Authorization` header. The unauthenticated webhook also allows preview creation. The target must be a `dbt Cloud IDE` project and the attacker must know its `projectUuid`; the UUID is not enumerable but can be discovered in shared or multi-tenant contexts. Version 0.3214.0 fixes identifier path traversal and verifies webhook HMAC signatures only when a secret is configured; without a secret, unsigned webhooks continue to be processed.