As already mentionoed this is your change address.
This was a small 'bug' in an older version of the ledger nano s.
I would advise you to update your software.
Current versions:
Bitcoin Chrome: 1.10.1
Bitcoin app (on your nano s): 1.1.18
Firmware: 1.3.1
The new "attack" is replacing your recieving address in the GUI of your application.
Ledger already has a workaround ready where you have to confirm your recieving address ony our nano S.
Note: The attack vector covers the GUI of your wallet. Not the wallet / the nano s itself.
Everything you confirm on your nano s can be considered as verified and safe.