If you would like to ensure that subscriptions do not happen involuntarily you can enable Double Opt-in, which requires users to confirm in an automated email their subscription to any group after they submit the Profile.

The option to do this can be found under the Administration –> CiviMail → CiviMail Component settings tab. By checking the ‘Enable Double Opt-in for Profile Group(s) field’ field any subscription to Groups will have an additional step of confirmation from your contacts.

If the option is enabled contacts who submit the Profile and choose to subscribe to a group will see a notification that they will receive an email where they have to confirm their subscription

The mail by default has the following simple format:

Once the user clicks on the link they are directed to a system page stating they have been added to the group they subscribed to and they will be listed in the contact list of the Group.

Until the contact clicks on the link to confirm their subscription they will be listed with ‘Pending’ status in the Group.