app/views/journals/index.builder in Redmine before 2.6.9, 3.0.x before 3.0.7, and 3.1.x before 3.1.3 allows remote attackers to obtain sensitive information by viewing an Atom feed.
https://github.com/redmine/redmine/commit/7e423fb4538247d59e01958c48b491f196a1de56