What does this mean? For those who don’t want to be bogged down by the technical details, basically this means that if you played any Blizzard game, there was a security vulnerability that could have allowed hackers to remotely hijack the Blizzard Update Agent tool and use it for their own purpose, such as installing malicious files, accessing network drives, and so on.
https://twitter.com/taviso/status/955540415263907840
One of the main reasons why all of Blizzard’s games are affected is because for the most part, they are launched via the Battle.net Launcher (for PC gamers), which presumably means that they all use the Blizzard Update Agent tool. As Ormandy points out, Blizzard is boasting that they have 500 million monthly active users, meaning that quite a number of gamers out there are affected.
However the good news is that Blizzard seems to have issued a short-term fix for the issue, and have told Ormandy that a more robust fix is in the works that will be released soon.