This is a bash script for updating casks pre-"brew cask upgrade" cmd. It catches all version mismatches missed by official cask upgrade methods by doing it manually.

cask-upgrade.sh

#!/bin/bash

# USE AT YOUR OWN RISK.

# This is a bash script for checking brew cask versions and reinstalling if 
# there is a version mismatch. Obviously this may revert casks that have self 
# updating to previous version, but then it is as easy as simply updating the 
# repo with the cask-repair command. This way the community gets the updates 
# too. 


brew cask cleanup
brew update

for c in $(brew cask list); do
  cask_name=$(echo $c);
  cask_ver_local=$(brew cask list $c --versions | cut -d " " -f2);
  cask_ver_current=$(brew cask info $c | head -n 1 |tr -d ':' | cut -d " " -f2)
  echo "------------"
  echo $cask_name
  echo "Current installed version:          $cask_ver_local"
  echo "Version avaliable via cask instalL: $cask_ver_current"

  if [ "$cask_ver_local" != "$cask_ver_current" ]; then
    echo "...Updating $c to latest"
    brew cask reinstall $c
  fi 
done