GHSA-x36r-4347-pm5x: swagger-typescript-api vulnerable to Server-Side Request Forgery via spec `$ref`

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: // 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 Set<string>(); const queue = [this.stripHash(this.config.url)]; while (queue.length > 0) { const currentUrl = queue.shift(); if (!currentUrl || visited.has(currentUrl)) continue; visited.add(currentUrl); if (this.externalSchemaCache.has(currentUrl)) continue; const schema = await this.fetchRemoteSchemaDocument(currentUrl); // <-- HTTP GET if (!schema) continue; this.externalSchemaCache.set(currentUrl, schema); for (const ref of this.extractRefsFromSchema(schema)) { const normalizedRef = this.normalizeRef(ref); if (normalizedRef.startsWith("#")) continu