Samsung Galaxy S Duos (GT-S7566) Firmware Overview
What is the latest GT-S7566 firmware?
S7566ZCAMH1, released October 1, 2013 with Android 4.0. The archive holds 2 official builds across 1 region (CSC). Each one is the full stock ROM (flash file) for Odin, not an OTA patch.
Is the Samsung Galaxy S Duos still getting updates?
Most likely not: there has been no new firmware since October 2013, so Android 4.0 is the last version this model got. The final builds below are still the best choice for a clean reinstall.
All GT-S7566 firmware builds
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. Use HOME_CSC to keep your data, CSC for a full wipe.