Make WP plugins work

In wp-config.php:

if(is_admin()) {
   add_filter('filesystem_method', create_function('$a', 'return "direct";' ));
   define( 'FS_CHMOD_DIR', 0751 );
}

Set healthy permissions:

chown www-data:www-data  -R * # Let Apache be owner
find . -type d -exec chmod 755 {} \;  # Change directory permissions rwxr-xr-x
find . -type f -exec chmod 644 {} \;  # Change file permissions rw-r--r--