Leap42.3-64, KDE, Firefox 60.0.1

I have a collection of URLs organized in a .doc file.

When I copy and paste a URL from the .doc file, over the URL in an existing firefox tab , the copied paste string gets over written by the original firefox tab URL.

I think this might be an artifact of a password manager I was using previously under leap 42.2 but no longer use. It had an automated password fill-in function. I forget the name of it.

Is anyone familiar with this, how do I turn it off?

Thank you.