While upgrading WordPress running on Microsoft Windows Server 2012 R2 from 4.6 to 4.7, I ran into error about file permission. In short, TEMPORARILY add WRITE security permission to IIS_IUSRS local group for wordpress folder Run upgrade successfully, then Remove WRITE security permission of IIS_IUSRS local group from wordpress folder. WordPress: Temporary security persmission settings to upgrade Downloading update from https://downloads.wordpress.org/release/wordpress-4.7-new-bundled.zip … Unpacking the update… The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.: wp-admin/includes/update-core.php Installation Failed Check PHP error log: C:\Windows\Temps\PHP70x64_errors.log [19-Dec-2016 12:04:29 UTC] PHP Warning: copy(C:/wordpress/wp-admin/includes/update-core.php): failed to open stream: Permission denied in C:\wordpress\wp-admin\includes\class-wp-filesystem-direct.php on l