Comment 9 for bug 1173457

I agree that this bug is critical. It happened to me as well with Ubuntu 17.10 and took me a while to clean up my disk.
I read afterwards that there are some options to the installer, like the --removable, but I think they are not relevant. I didn't know about these options when I decided to install Ubuntu, and the default, out of the box, "happy-path" for the user (me) presents an option to avoid touching the internal HDD but at the end it still touches it.
I can say in all fairness that I've lost my trust in Ubuntu because of this and I definitely won't try installing it again without a very strong assurance that this problem is for sure gone.