I setup a fresh install of wikijs because I had some problems with the old one. Moved over all content to the new instance and everything was working fine. Except...now 2 weeks later I noticed I forgot to remove the read permissions from the guest group and everyone had access to all data.

I know that it is the responsibility of the administrator to take care of such things. But in my opinion the default setting should be the safest option (No read permission) as wikijs is not only used for public wikis but also for internal stuff.