Space age dlc is transferring to other steam accounts.

[M0ssley]

I went to visit my parents, and logged into steam on my dad's computer to play factorio. After I finished playing and logged out so he could play factorio on his steam account, we found that he had access to the space age dlc despite never purchasing it through steam. It seems that once space age was played on that computer, it was giving him access to it now that it is downloaded on his computer from when I was playing it.