
Samsung GALAXY Tab
The latest firmware for Samsung GALAXY Tab (GT-P1000M) is P1000MUGKF6 with Android 2.3.3 (Gingerbread), released on June 20, 2011 for 1 region (CSC). Every official firmware build for GT-P1000M, 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/P1000MUGKF6

GT-P6810

GT-P6211

GT-P6210

GT-P6200

GT-P1010

GT-P1000N

GT-P7320T

GT-P7310
You can find the firmware on the model: GT-P1000M page.
Yes, all firmware files for GT-P1000M are 100% official, original, and obtained directly from Samsung servers.
To flash GT-P1000M, 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 GT-P1000M.