Is amazon.com allowing authentication based on browser cookies only?

So I found out a couple of days ago that amazon.com has changed its behavior when trying to make a purchase. For years and up until recently, I could open a browser, log into amazon, close the browser. When I would open the browser again and direct it to amazon, the site would know my account but not allow me to check out without providing the password first. This allowed other people in the house to watch prime videos but not abuse my account and make unauthorized purchases. This apparently changed last week. Now, if I use amazon and close the browser without logging out or clearing cookies, then whoever uses the same browser after me can make purchases without being prompted for a password! I don’t have 1-click enabled anywhere, my browser doesn’t have the password stored, and auto sign-in is disabled. Tried this in Firefox and Chrome to the same effect.

Has anyone else experienced this, particularly on Windows? My main concern is that this is a security issue on shared computers. Is this supposed to be a new feature (I don’t want it…)?