Oauth-proxy: open redirect via /\ and /\t bypass in post-login redirect

A flaw was found in oauth-proxy. The application fails to properly validate the destination redirect parameter (`rd`) during post-login redirection. A remote attacker can exploit this vulnerability by enticing a user to follow a specially crafted link, resulting in the user being redirected to an arbitrary external website after authenticating. This open redirect can be leveraged to conduct phishing attacks or credential theft.