Impact
Authorization headers on requests are sensitive information. On making a request using the https scheme to a server which responds with a redirect to a URI with the http scheme, we should not forward the Authorization header on. This is much the same as to how we don’t forward on the header if the host changes. Prior to this fix, https to http downgrades did not result in the Authorization header being removed, only changes to the host.
Patches
Affected Guzzle 7 users should upgrade to Guzzle 7.4.4 as soon as possible. Affected users using any earlier series of Guzzle should upgrade to Guzzle 6.5.7 or 7.4.4.
Workarounds
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.
References
For more information
If you have any questions or comments about this advisory, please get in touch with us in #guzzle on the PHP HTTP Slack. Do not report additional security advisories in that public channel, however – please follow our vulnerability reporting process.