Checking for permission issues

I was having some issues earlier with updates which required me to temporarily change some permissions on system files. I believe all permissions are restored, but I want to check this.

Is there a way to check if Nextcloud is leaking any files to users that are not logged in, or if Apache is doing this? Such as navigating to

I did some research and it looks like if returns a 403 error the data is safe, but in my case it just redirects back to the login page.

These are the permissions on my nextcloud data folder: drwxrwx— 5 www-data www-data

Appreciate any insight on this, thanks!