Answer
You can limit the visibility of your contact list in your privacy settings.
- Click on Settings in the top right corner of the XING website.
- Choose Settings.
- Click on Privacy.
- In the section Your profile you can now choose under Contact list whether you want to make your list of contacts visible to nobody, my direct contacts only, contacts and their contacts or all (members and recruiters).
(In the XING app click on your profile image -> Settings -> XING Settings -> Privacy -> Contact list)