Tornado before 3.2.2 sends arbitrary responses that contain a fixed CSRF token and may be sent with HTTP compression, which makes it easier for remote attackers to conduct a BREACH attack and determine this token via a series of crafted requests.
https://github.com/tornadoweb/tornado/commit/1c36307463b1e8affae100bf9386948e6c1b2308
https://bugzilla.redhat.com/show_bug.cgi?id=1222816
https://bugzilla.novell.com/show_bug.cgi?id=930362