Samsung Galaxy Y Plus (GT-S5303) Firmware Overview
The archive lists 2 official builds for the Samsung Galaxy Y Plus across 1 region (CSC). The newest one is S5303XXAMK1, released November 15, 2013 with Android Cream.
How to Flash GT-S5303 Firmware
Put the Samsung Galaxy Y Plus 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.