Guzzle, an extensible PHP HTTP client. Authorization and Cookie headers on requests are sensitive information. In affected versions on making a request which responds with a redirect to a URI with a different port, if we choose to follow it, we should remove the Authorization and Cookie headers from the request, before containing. Previously, we would only consider a change in host or scheme. Affected Guzzle 7 users should upgrade to Guzzle 7.4.5 as soon as possible. Affected users using any earlier series of Guzzle should upgrade to Guzzle 6.5.8 or 7.4.5. Note that a partial fix was implemented in Guzzle 7.4.2, where a change in host would trigger removal of the curl-added Authorization header, however this earlier fix did not cover change in scheme or change in port. An alternative approach would be to use your own redirect middleware, rather than ours, if you are unable to upgrade. If you do not require or expect redirects to be followed, one should simply disable redirects all together.