For a lot of european users that need to use whatsapp for his net-effect:

Whatsapp has just put an apk on his website with a sign never used before. There are three possible explaination:

1) They have been hacked and someone has put a compromised whatsapp apk on the website. Dont install before the situation will be more clear.

2) A test apk with a test sign has been erroneosly putted on the website. They never done that before as I know. Still dont install now if you dont want to need to uninstall-reinstall a second time for next update.

3) They have someway decided to switch signature, maybe the old one has been compromised.