HoloViz Panel from 1.2.2 before 1.9.0 Open Redirect via next Parameter

HoloViz Panel from 1.2.2 before 1.9.0 contains an open redirect vulnerability in panel/auth.py that allows remote attackers to redirect users by supplying an unvalidated next query parameter. BasicLoginHandler and PasswordLoginHandler store the parameter in a next_url cookie, so crafted login links send victims to attacker-controlled external sites after successful login.