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.
Jenkins Visualworks Store Plugin 1.1.3 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.