To make this work you take your open source Firefox and download the Adobe Content Decryption Module (CDM) - a closed source ''black box''. Who knows what is in there, maybe Adobe took some dollars from the NSA and put some spyware in there -- you can't tell because the channel to download the video is encrypted. Maybe they have also taken some rubles and inserted some code from the FSB (KGB successor) and maybe from elsewhere ?
Who knows ? I don't -- it is closed source.