github.com/sylabs/scs-library-client is the Go client for the Singularity Container Services (SCS) Container Library Service. When the scs-library-client is used to pull a container image, with authentication, the HTTP Authorization header sent by the client to the library service may be incorrectly leaked to an S3 backing storage provider. This occurs in a specific flow, where the library service redirects the client to a backing S3 storage server, to perform a multi-part concurrent download. Depending on site configuration, the S3 service may be provided by a third party. An attacker with access to the S3 service may be able to extract user credentials, allowing them to impersonate the user. The vulnerable multi-part concurrent download flow, with redirect to S3, is only used when communicating with a Singularity Enterprise 1.x installation, or third party server implementing this flow. Interaction with Singularity Enterprise 2.x, and Singularity Container Services (cloud.sylabs.io)…