Being a user myself for more than 10 years, I just noticed an official statement published on their service health page.
Although they report that the hacker gained access to all the EU client list (including salted SHA512 passwords) , it appears the main goal was to gain access to their canadian net-install servers.
European clients are strongly advised to modify their OVH manager password.
More infos on the hack in the link (translated)"
Link to Original Source