I terminated the employment contract of one admin after I saw him setting system folders world writeable.

Mitäkuuluu is executed with User=nemo Group=privileged privileges and permission set u=rwx,g=rx,o=rx is correct for .whatsapp directory. Since v0.1-25 that directory has had group privileged and it's owned by nemo as earlier.

Files and directories under .whatsapp shall be writable by nemo user only and owned by nemo. Group differs and can be nemo or privileged depending on file.