Is it not in the repos yet? I noticed there are blogs and articles about 26 being released and one should be able to upgrade to 26. But, it's not even displayed in 14.04 (13.10 shows in my install)?
Code:
$ apt-cache policy firefox
firefox:
Installed: 25.0+build3-0ubuntu0.13.10.1
Candidate: 25.0+build3-0ubuntu0.13.10.1