Thanks for the heads-up on this. The above-linked TechCrunch article links a
Guardian article by Cory Doctorow that I found very informative.
Looking at the
firefox 38.0 binary releases, the dual versions exist for Windows only. Made me wonder if the Linux versions contain the offending software or not. The Guardian article mentions that Adobe's blob is also available for Linux, so perhaps they could.
But
this article says the EME/DRM support is just on Windows now. I also found some conflicting info on this point elsewhere so I'm not 100% sure.
Maybe I'll just stop downloading FF, I don't really use it anyway. Though I suppose SeaMonkey for Linux may be at risk in the future.