Well, this is huge, so I'd like to draw your attention to what's happening right now. This is a very alarming case, and it concerns every ad blocker user.
Brief introduction into ad blocking
To understand better what's happened, you should first learn a bit more about ad blocking. Every ad blocker work is based on using so-called filters lists, which are maintained (mostly) by volunteers. That said, whichever ad blocker you use, credits for actual ad blocking belong to the filter lists maintainers. The most popular filters list is called EasyList and this is what this story is about.