A Puppet 'Fact' which returns a comma separated list of hotfixes installed on a windows machine.

hotfixes.rb

require 'facter'

Facter.add(:hotfixes) do
  confine :operatingsystem => :windows
  setcode do

    require 'facter/util/wmi'

    fixes = []

    wmi = Facter::Util::WMI.connect()
    wmi.ExecQuery("select HotFixID from win32_quickfixengineering").each do |hotfix|
      fixes.push(hotfix.HotFixID)
    end

    fixes.sort.join(',')
  end
end