The history-clearing feature in Safari in Apple iOS before 7 does not clear the back/forward history of an open tab, which allows physically proximate attackers to obtain sensitive information by leveraging an unattended workstation.
http://archives.neohapsis.com/archives/bugtraq/2014-10/0101.html
http://lists.apple.com/archives/security-announce/2013/Sep/msg00006.html
https://support.apple.com/kb/HT6535