The Keyboards component in Apple iOS before 5 displays the final character of an entered password during a subsequent use of a keyboard, which allows physically proximate attackers to obtain sensitive information by reading this character.
https://exchange.xforce.ibmcloud.com/vulnerabilities/70555
http://support.apple.com/kb/HT4999
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html