From Matt Mullenweg:
Tough note to communicate today: Automattic had a low-level (root) break-in to several of our servers, and potentially anything on those servers could have been revealed.
We have been diligently reviewing logs and records about the break-in to determine the extent of the information exposed, and re-securing avenues used to gain access. We presume our source code was exposed and copied. While much of our code is Open Source, there are sensitive bits of our and our partners’ code. Beyond that, however, it appears information disclosed was limited.
When was the last time you changed your password? It’s about time, do it today.