The Sidebar Link plugin allows users able to configure jobs, views, and agents to add entries to the sidebar of these objects. There was no input validation, which meant users were able to use javascript: schemes for these links.

Jenkins Sidebar Link Plugin 2.2.1 and earlier does not restrict the path of files in a method implementing form validation, allowing attackers with Overall/Read permission to check for the existence of an attacker-specified file path on the Jenkins controller file system.