Права доступа к папкам 755 и файлам 644

Все папки должны иметь права 755 или 750.
Все файлы должны иметь права 644 или 640.

https://codex.wordpress.org/Changing%20File%20Permissions

All directories should be 755 or 750.
All files should be 644 or 640. Exception: wp-config.php should be 440 or 400 to prevent other users on the server from reading it.
No directories should ever be given 777, even upload directories. Since the php process is running as the owner of the files, it gets the owners permissions and can write to even a 755 directory.