Independent researcher Indrajeet Bhuyan has demonstrated that is possible to crash the popular messaging app Whatsapp by sending crazy smileys. The trick works on both WhatsApp Web and mobile app. The impact is serious if we consider that up to 1 Billion users are affected by the problem. Users that are victims of this specific attack have to open their Whatsapp client and delete the whole conversation with the attacker in order to use whastapp normally. The attack has a different effect against iphone devices, in fact, it fails to crash application but it just freezes it for a few seconds.”]
Source: https://securityaffairs.co/wordpress/42977/hacking/crash-whats-app-smileys.html