groups_access_member_info
The
groups_access_member_info permission allows your app to read publicly available group member information like name and ID if the post author has granted your app access. The allowed usage for this permission is to add user details to content posted in their group and help group admins to collect insights about activity happening in their group. You may also use this permission to request analytics insights to improve your app and for marketing or advertising purposes, through the use of aggregated and de-identified or anonymized information (provided such data cannot be re-identified).