The issue is related to how an http.Client handles HTTP redirects. When an HTTP redirect is made to a domain that is not a subdomain match or exact match of the initial domain, sensitive headers such as `Authorization` or `Cookie` are not forwarded. However, a maliciously crafted HTTP redirect could cause these sensitive headers to be unexpectedly forwarded. For example, a redirect from foo.com to www.foo.com will forward the `Authorization` header, but a redirect to bar.com will not.