"Updated" search bar with Bing search appeared in Tabs today & I can't get rid of it!

Question

PROBLEM SOLVED! This is so embarrassing, but here's what fixed it. I'll leave the question here in case others download the add-on and can't figure out why it's doing what it's doing, but if a mod wants to delete the question I won't mind.
Anyhow, I right clicked on exactly the right spot on the bar and chose Delete, which brought up the add-on tab, which showed an add-on called "Default Tab," restarted Firefox, and now both behaviors are gone--no more search window in the tab bar, and no more search box in new tabs. I must have thought Default Tabs sounded cool, but didn't expect it to do what it did.
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Sometime between Friday and this morning a new search box¬ appeared in Firefox that called itself the “Updated Search Bar” until I tried it the first time. I’d like to avoid resetting Firefox, but if that’s the only way to fix this I guess I’ll have to. All suggestions are welcome.
The box looks much like the default search box except that it has a big orange button on the right saying "Search." It’s located in the tab bar, next to the last tab, taking up valuable real estate if I have more than 4 or 5 tabs open, which I often do. The default “search” is Bing, the other options are things like Facebook and Twitter, and it has no option to manage search engines. It doesn’t appear in my extensions or plugins, and I can’t find information about it anywhere.
BTW, my old search box is still in the navigation bar, and although I haven’t been able to get rid of Bing for the “search” search, I’ve made DuckDuckGo the default by moving it to the top of the list.
Thanks for reading!

Answer 1

PROBLEM SOLVED (see above)
Oh, and now if I open a new tab it has a Bing search bar. Grr!