Server-side request forgery via $ref HTTP resolution in github.com/go-openapi/spec. The default document loader fetches any URL found in a $ref field with no restriction, so expanding a specification from an untrusted source can reach internal cloud metadata endpoints, private network addresses and localhost services. This is inherent to the default configuration and is not fixed by a code change; the mitigation is to inject a confined loader via ExpandOptions.PathLoaderWithOptions (loading.WithHTTPClient) or to use the restricted loaders in github.com/go-openapi/loads.