
Samsung Galaxy A8
Every official firmware build for SM-A800X, newest first: one row per build with all regions (CSC) that received it.
Specifications of SM-A800, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-A800YZ

SM-A805N

SM-A700X

SM-A810F

SM-A908N
You can find the firmware on the model: SM-A800X page.
Yes, all firmware files for SM-A800X are 100% official, original, and obtained directly from Samsung servers.
To flash SM-A800X, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing SM-A800X.