On my mid 2011 iMac, when using the “Firefox” browser, I click on a link and instead of opening a new tab (Prefs is set this way), 99% of the time it opens a new webpage.

All of a sudden, within the last 6 months, this began happening. When I usually click on a link, or if I right click on a link and select “open new tab” option, a new webpage will open instead of a new tab. So I copy the new webpage and paste the link in a new tab in the original webpage and then I have to delete the new window or else I have a screen full of webpages with only one tab. Clutter clutter clutter!

I reinstalled the Firefox App, and no change. Turned my iMac on/off, no change.

Suggestions?