An issue was discovered in GitLab 10.7.0 and later through 12.9.2. A Workhorse bypass could lead to job artifact uploads and file disclosure (Exposure of Sensitive Information) via request smuggling.
GitLab EE/CE 8.11 to 12.9 is leaking information on Issues opened in a public project and then moved to a private project through Web-UI and GraphQL API.