Jenkins Git Client Plugin 2.8.4 and earlier and 3.0.0-rc did not properly restrict values passed as URL argument to an invocation of 'git ls-remote', resulting in OS command injection.

Git Plugin connects to a user-specified Git repository as part of form validation. An attacker with no direct access to Jenkins but able to guess at a username/password credentials ID could trick a developer with job configuration permissions into following a link with a maliciously crafted Jenkins URL which would result in the Jenkins Git client sending the username and password to an attacker-controlled server.