Check the file for any trailing hidden data using binwalk -e . Conclusion
Open the file in a hex editor (like HxD or Ghex ). Ensure the header starts with the standard 7z signature: 37 7A BC AF 27 1C 00 03 gt00.7z
Running file gt00.7z confirms it is a 7-zip archive data. Check the file for any trailing hidden data using binwalk -e