In an effort to reduce spam and spread of misinformation, WhatsApp today announced a new privacy control feature that will allow you to control who can add you to group chats.
This new feature is available under Settings > Account > Privacy > Groups, where you can select one of three options: “Nobody”, “My Contacts”, or “Everyone”. With “Nobody”, you need to approve joining every group to which you’re invited, and with “My Contacts”, only people you have in your address book can add you to groups. Any group invite you receive will have three days validity before it expires.
This new privacy feature will begin rolling out to some users starting today and will be available worldwide in the coming weeks.
Source: WhatsApp