@ kl522

I don't know of a changelog, but this DstroWatch table lets you compare 6.7 with previous versions:
http://distrowatch.com/table.php?distribution=knoppix

This table indicates Firefox 5 to be an option with 6.7.
I was unable to verify Firefox 5 as an option with my CD version of 6.7, even opening up all possible repositories.
I had found Firefox 5 to have a few problems in Ubuntu Unity, so I'm not that anxious about this.
For example, it would not retain preference changes in font maxes & mins and disabling of url underlines.