Atlassian has published the following security statement for providing cloud services that you can find at the following link: https://www.atlassian.com/trust/policies/cloud-security
External Share for Confluence app STORES ONLY DATA provided by an Atlassian instance when installing the add-on. This data contains basic information for validating and enabling communication with a particular Atlassian instance.
Effective as of 14th October 2019.