Samsung Galaxy S Duos (GT-S7566) Firmware Overview
The archive lists 2 official builds for the Samsung Galaxy S Duos across 1 region (CSC). The newest one is S7566ZCAMH1, released October 1, 2013 with Android Cream.
How to Flash GT-S7566 Firmware
Put the Samsung Galaxy S Duos into Download Mode, load the BL, AP, CP and CSC files into Odin on a Windows PC and press Start. Pick a build with the same or a higher Bit than the one installed — a lower bootloader binary will be rejected.