Viewing known file extensions is disabled by default on Windows 10, this default setting is commonly used by criminals to mask very dangerous files disguised as harmless file types.
1. Click on the Start button in the task bar
2 – Open the Control Panel.
3 – Click Appearance and Personalization, choose File Explorer Options.
4 – In the File Explorer Options window that opens, click the View tab.
5 – Deselect Hide file extensions for known file types and click OK.
From this point on Windows 10 Operative system will show file extensions for any file on your system, allowing you to visually identify the potential threat level of that file you are about to click.