Today two users were added to a group and our apps have received non-stop notifications (more than 99+) for each user. This happened for both platforms. Based on the screenshots more than 16k notifications were sent. 5k to iOS and 11k for Android.
Currently to disable the spamming of notifications to our users, I have deleted the auth key in Firebase Console. Can you clarify this issue from your end? This only happened for the group action message but not for notifications for Text Messages.
User @ Group Name
User was added to group "Group Name"
(see attached screenshot)