Notice that since their last move WhatsApp can’t read messages content anymore, but they can still observe a lot of plain metadata :
- numbers <-> real names.
- every group description & image.
- every message timestamp, length, and status (missing, delivered, read).
- every conversation participants.
- every muted user / group.
- online users and timestamps (when everyone’s online).
- hesitation in message writing (they still know when you are actually typing before sending a message).
- objects types (picture, location, video, etc.)