The original post was regarding firefox dropping alsa, and on Vector linux 7.2 appears puse audio is included so firefox 52 should and does have sound.
I extracted firefox 52.0.2 from mozilla to /opt as nightflier posted, then added a link to open as user from fluxbox menu. or you could use an icon.
before opening firefox I deleted the ./mozilla folder from the home directory.
I then opened firefox, created a link for netflix and signed in to netflix. it ask to apply drm for the site ( or you can toggle from preferences/content). widevine was installed.(a pop up said to try the site later as it was installing.
I then reopened the browser and signed into netflix and started watching a show.
deleting the ./mozilla folder from home solved the previous error on netflix that I was not using an official mozilla browser.
this is on vector linux light 32 bit without flash listed in the plugins. On acer one netbook with 1 gig ram. I was also able to watch youtube videos. I could benefit from a little more ram.
as flash may be required for some sites or users I suggest using the latest flash-plugin 25. I am not sure how to install it to firefox in this particular situation.
edit: actually all I did was install flash 25 with installpkg and now can watch video on sites that require flash.
thought I would update my findings...Sorry for going off topic.