app/views/timelog/_form.html.erb in Redmine before 2.6.8, 3.0.x before 3.0.6, and 3.1.x before 3.1.2 allows remote attackers to obtain sensitive information about subjects of issues by viewing the time logging form.
https://www.redmine.org/issues/21150
https://github.com/redmine/redmine/commit/c096dde88ff02872ba35edc4dc403c80a7867b5c