Icinga Web 2 is an open source monitoring web interface, framework and command-line interface. A vulnerability in versions prior to 2.11.5 and 2.12.13 vulnerability allows an attacker to craft a URL that, once visited by an authenticated user (or one that is able to authenticate), allows to manipulate the backend to redirect the user to any location. This issue has been resolved in versions 2.11.5 and 2.12.3 of Icinga Web 2. No known workarounds are available.
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.