
Samsung Galaxy Tab 8.9
The latest firmware for Samsung Galaxy Tab 8.9 (SGH-I957) is I957UMLJ4 with Android 4.0.4 (Ice Cream Sandwich), released on November 7, 2012 for 1 region (CSC). Every official firmware build for SGH-I957, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/I957UMLJ4

SGH-I927

SGH-S730M

SGH-T999N

SGH-T989D

SGH-T859
You can find the firmware on the model: SGH-I957 page.
Yes, all firmware files for SGH-I957 are 100% official, original, and obtained directly from Samsung servers.
To flash SGH-I957, 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 SGH-I957.