sigstore-js provides JavaScript libraries for interacting with Sigstore services. Prior to 0.7.2, packages/oci/src/registry.ts contains a RegistryClient.signIn() method that stores registry Authorization and Docker configuration headers as defaults on a shared HTTP client, while RegistryClient.uploadBlob() sends a fresh PUT to an absolute blob-upload Location supplied by the registry without checking that its origin or scheme matches the registry. A malicious or compromised registry can therefore direct a user pushing an artifact through attachArtifactToImage() to an attacker-controlled host and receive the registry bearer token, Basic credentials, or custom authentication headers. Redirect-time header stripping does not prevent the leak because the cross-host PUT is a new explicit request rather than a followed redirect. This is a residual of CVE-2026-59891, whose fix changed credential selection in credentials.ts but did not constrain where credentials are sent from registry.ts. Version 0.7.2 fixes the issue by separating registry credentials from client-wide defaults and sending them only to the registry origin.