swagger-typescript-api generates API clients for Fetch or Axios from OpenAPI specifications. Prior to 13.12.2, src/resolved-swagger-schema.ts warmUpRemoteSchemasCache resolves external $ref URLs and fetchRemoteSchemaDocument uses isHttpUrl to fetch any http or https target without private IP, redirect, DNS rebinding, or same-origin validation, allowing an attacker-controlled OpenAPI spec to make the generator issue requests to internal or link-local services. This issue is fixed in version 13.12.2.

Affected: npm: swagger-typescript-api

### Summary

`swagger-typescript-api` walks every `$ref` value in the input OpenAPI spec and, for any `$ref` whose target is an `http(s)://` URL, issues an HTTP GET to that URL during generation (`warmUpRemoteSchemasCache`). The only URL filter is a regex that matches `^https?://` — there is **no private-IP allowlist, no DNS-rebinding protection, no redirect cap, and no same-origin check against the spec source**. A malicious OpenAPI spec can therefore force the generator process to issue HTTP requests to arbitrary hosts and paths reachable from the generator's network, including `127.0.0.1`, RFC-1918 ranges, internal hostnames, and the cloud instance-metadata endpoint at `169.254.169.254`.

The attacker model is identical to the previously reported code-injection findings: a developer or CI pipeline that runs `swagger-typescript-api generate` against an attacker-controlled spec (remote URL, third-party / public OpenAPI registry, multi-tenant tenant input, or a spec file modified via PR).

### Details

`SwaggerSchemaResolver.fetchSwaggerSchemaFile` (`src/swagger-schema-resolver.ts:122`) loads the entry-point spec. After it parses, `ResolvedSwaggerSchema` (`src/resolved-swagger-schema.ts`) calls `warmUpRemoteSchemasCache` which does a BFS over every external `$ref`:

```ts // src/resolved-swagger-schema.ts:399-445 private async warmUpRemoteSchemasCache() { if (typeof this.config.url !== "string" || !this.isHttpUrl(this.config.url)) { return; } const visited = new Se…