The Precious module in gollum before 4.0.1 allows remote attackers to read arbitrary files by leveraging the lack of a certain temporary-file check.
https://github.com/gollum/gollum/issues/1070
https://github.com/gollum/gollum/commit/ce68a88293ce3b18c261312392ad33a88bb69ea1
http://www.openwall.com/lists/oss-security/2015/09/22/12