a friend of mine played with my mac and set
chmod 0755 on
/ (I disabled SIP).
Now the Guest user can see every document on my filesystem and so everybody having physical access to my MacBook would be able to copy my stuff onto another machine.
Both starting the "first aid" function of El Capitan and upgrading to 10.11.3 didn't help.
I'm a bit scared of setting
Could an El Capitan user with correct permissions run
cd /; ls -lah and paste the results?
Could the same be done for
/Users and if yes, how?