PostgreSQL before 9.0.19, 9.1.x before 9.1.15, 9.2.x before 9.2.10, 9.3.x before 9.3.6, and 9.4.x before 9.4.1 allows remote authenticated users to obtain sensitive column values by triggering constraint violation and then reading the error message.
http://www.debian.org/security/2015/dsa-3155
http://www.postgresql.org/about/news/1569/
http://www.postgresql.org/docs/9.4/static/release-9-4-1.html
http://www.postgresql.org/docs/current/static/release-9-0-19.html
http://www.postgresql.org/docs/current/static/release-9-1-15.html
http://www.postgresql.org/docs/current/static/release-9-2-10.html
http://www.postgresql.org/docs/current/static/release-9-3-6.html