You can't find it.
The term Xerox uses is Spar Software.
It is nothing like Beta software, but most look at it that way, at a time it pretty much was.
Now days things change pretty fast, and when they do, things break, sometimes really common things break, sometimes a weird workflow causes an issue for a single company. Xerox tends to release the fixes for everything in a new firmware. That would be a spar firmware. They don't post them to Xerox.com for casual browsing because they don't want people with perfectly fine machines installing things just because . Think of it like the motto.
If it ain't broke, don't fix it
If it is broke, definitely fix it.
Officially you are supposed to call in, get to 2nd level support, explain the issue, do the testing, get the spar.
I just happen to work here, there is no "voided warranty" concerns or anything.