@hnahli there is no straight forward option to add the restriction. you will have to modify core.
Removing Restrictions from Guests
Is there a way to allow guests to vote :1+: And upload photos
I understand that it is not polite to ask a second time, but I am afraid that my question was not properly understood ...
I ask the experts if it is possible to remove restrictions from the guests.
I want guests to be able to like my posts and give likes
I also want them to be able to upload photos in the posts they edit
May prove illuminating? I'm not on latest nodebb but think you can restrict guests to uploading photos. I don't note any knobs for up/down voting though. Hmmm..... Maybe in more recent versions?
Be all that as it may, have you thought this through?