Multiple open redirect vulnerabilities in Jenkins before 2.3 and LTS before 1.651.2 allow remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via unspecified vectors related to "scheme-relative" URLs.
https://www.cloudbees.com/jenkins-security-advisory-2016-05-11
https://wiki.jenkins-ci.org/display/SECURITY/Jenkins+Security+Advisory+2016-05-11