Upgrading Firefox fails. lzma error: compressed data is corrupt

Here's how I fixed it.

cd  /var/cache/apt/archives
sudo rm firefox_32.0+build1-0ubuntu0.14.04.1_i386.deb
sudo apt-get update
sudo apt-get upgrade

You need to remove the broken package in the archives directory then update and install firefox.

sudo apt-get autoremove
sudo apt-get update
sudo apt-get install firefox

apt clean fixed that problem for me on a Ubuntu 18.04.