Manually, perhaps because the attacker crafts the messages to make that desirable. But a bigger concern is automatically. WhatsApp for example can automaticall

Manually, perhaps because the attacker crafts the messages to make that desirable. But a bigger concern is automatically. WhatsApp for example can automatically save all received photos to your Camera Roll, which is of course automatically backed up to iCloud for many people. So an attacker could potentially just send you a bundle of 40 images of however many and your phone automatically sends it to Apple.