Its a problem yes,but you can check it on
https://www.apkmirror.com/apk/whatsapp-inc/whatsapp/whatsapp-messenger-2-25-35-73-release/
and click on 'Verified safe to install (read more)'
then it should open a dialog with:
APK certificate fingerprints
SHA-1: 38a0f7d505fe18fec64fbf343ecaaaf310dbd799
SHA-256: 3987d043d10aefaf5a8710b3671418fe57e0e19b653c9df82558feb5ffce5d44
Certificate: CN=Brian Acton, OU=Engineering, O=WhatsApp Inc., L=Santa Clara, ST=California, C=US