Two recent Boston University computer engineering graduates revealed software and hardware hacks against the latest versions of the popular Square Reader. The researchers built an app that grabs the audio file and data, converts it and allows an attacker to replay the attack later on, over and over if they wish. Square has responded by deprecating older versions of Reader and they cannot be used with the Square Register app any longer. Square said in a statement the issue is with magnetic strip data and not its reader, nor its app.
Source: https://threatpost.com/researchers-unveil-square-reader-mobile-pos-hacks/114187/