Unsafe handling of user-specified cookies in treq

treq is an HTTP library inspired by requests but written on top of Twisted's Agents. Treq's request methods (treq.get, treq.post, etc.) and treq.client.HTTPClient constructor accept cookies as a dictionary. Such cookies are not bound to a single domain, and are therefore sent to *every* domain ("supercookies"). This can potentially cause sensitive information to leak upon an HTTP redirect to a different domain., e.g. should https://example.com redirect to http://cloudstorageprovider.com the latter will receive the cookie session. Treq 2021.1.0 and later bind cookies given to request methods (treq.request, treq.get, HTTPClient.request, HTTPClient.get, etc.) to the origin of the *url* parameter. Users are advised to upgrade. For users unable to upgrade Instead of passing a dictionary as the *cookies* argument, pass a http.cookiejar.CookieJar instance with properly domain- and scheme-scoped cookies in it.