GHSA-cxx3-hr75-4q96 Arcane Vulnerable to Unauthenticated Disclosure of Custom Compose Template Content (incl. `.env` secrets)

• Go github.com/getarcaneapp/arcane/backend: < 1.18.0 → fixed in 1.18.0

Summary Four `GET` endpoints under `/api/templates*` in Arcane's Huma backend are registered without any `Security` requirement, allowing any unauthenticated network client to list and read the full Compose YAML and `.env` content of every custom template stored in the instance. Because Arcane's UI exposes a "Save as Template" flow on the project / swarm-stack creation pages that persists the operator's *real* env content (database passwords, API keys, etc.) verbatim, this missing authorization is an unauthenticated read of operator secrets in practice — not a theoretical info-disclosure. The frontend explicitly treats `/customize/templates/*` as an authenticated area (`PROTECTED_PREFIXES` in `frontend/src/lib/utils/redirect.util.ts`), and every CRUD operation (POST/PUT/DELETE) on the same paths requires a Bearer/API key, so this is a clear backend authorization gap, not intended public access. Details Affected file: `backend/internal/huma/handlers/templates.go:194-228`. In `RegisterTemplates`, four `huma.Register` calls have no `Security:` block: ```go // templates.go huma.Register(api, huma.Operation{ OperationID: "listTemplatesPaginated", Method: "GET", Path: "/templates", ... // <-- no Security }, h.ListTemplates) huma.Register(api, huma.Operation{ OperationID: "getAllTemplates", Method: "GET", Path: "/templates/all", ... }, h.GetAllTemplates) huma.Register(api, huma.Operation{ OperationID: "getTemplate", Method: "GET", Path: "/templates/{id}", ... }, h.GetTemplate) huma.Register(api, huma.Operation{ OperationID: "getTemplateContent", Method: "GET", Path: "/templates/{id}/content", ... }, h.GetTemplateContent) ``` Arcane's auth bridge (`backend/internal/huma/middleware/auth.go:168-172`) only enforces authentication when the operation declares one of the security schemes (`BearerAuth` or `ApiKeyAuth`). With `Security` omitted, `parseSecurityRequirements` returns `isRequired=false` and the request flows through with no token check. `TemplateHandler.GetTemplateContent` (`templates.go:478-499`) calls `templateService.GetTemplateContentWithParsedData` (`backend/internal/services/template_service.go:1303-1347`), which returns the model's `Content`, `EnvContent`, parsed services, and parsed env-variable key/value pairs verbatim. The model `models.ComposeTemplate` (`backend/internal/models/template.go:15-16`) stores `Content` and `EnvContent` as plain `text` columns and has no owner / user binding. Impact • Pre-auth confidentiality breach. An unauthenticated client on the same network (or through any path-unaware reverse proxy) recovers the full `envContent` of every locally-stored Compose template. Because the supported "Save as Template" workflow takes the operator's real env values verbatim, this commonly includes database passwords, registry tokens, third-party API keys (Stripe, Sentry, etc.), and OIDC client secrets. • Internal asset enumeration. `GET /api/templates` returns names, descriptions, tags, and registry metadata for every template, leaking what services the team runs internally and which compose files they reuse