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.postgresql.org/docs/current/static/release-9-3-6.html
http://www.postgresql.org/docs/current/static/release-9-2-10.html
http://www.postgresql.org/docs/current/static/release-9-1-15.html
http://www.postgresql.org/docs/current/static/release-9-0-19.html
http://www.postgresql.org/docs/9.4/static/release-9-4-1.html