Second hand iPhone app security glitch
05 July, 2012
IF you have sold or traded-in your iPhone be warned your data may not be safe even though you think you have wiped it.The problem arises with certain apps, which use the phone’s unique ID (known as “UDID”) to log you in. In all fairness its not an iOS glitch but poor architecture on the developer's part.
We certainly wouldn't recommend only relying on UDID values as an authentication mechanism.