Note: 
Backup your files and database before upgrade.

Updation Steps:

1) Delete this folder from your server completely
->  "/core/library/filemanager/"

2) Goto this folder: "/Upgrade/v2.6 to v2.7/Upload"

3) Use your Server FTP or File Manager application on your server. 

4) Now, replace old files directly with new files present at upload directory.

You have done the work!