According to Verizon, no data was accessed by an external source, but at the end of the day, the data was exposed publicly and discovered by a security researcher.  I do not believe a definitive statement can be made as to who may or may not have discovered and harvested data.

I recommend every Verizon customer at least call Verizon support and change your pin.  You should also remain diligent in checking for unusual account activity.

https://www.tripwire.com/state-of-security/latest-security-news/14-million-verizon-customer-records-reportedly-left-exposed/

https://www.darkreading.com/cloud/verizon-suffers-cloud-data-leak-exposing-data-on-millions-of-customers/d/d-id/1329344

https://www.infosecurity-magazine.com/news/verizon-data-six-million-users/