Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control>(Mac=<Command>)<Shift> A)

In the Add-ons Manager, on the left, select Extensions. Remove Yahoo Anything. Now do the same in the computers Programs Folder.

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the "Applications" folder. Linux: Check your user manual.

After the problem is fixed, Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

dragonmagic said

I have been using Firefox for a while on win7. I bought a new win10 laptop and installed Firefox and am trying to figure out how to delete your FORCED yahoo search that was installed without my knowledge or permission. I can't get out of it and I can't open Firefox. I wouldn't mind using yahoo if it was a choice and not forced. I am totally not the only person who hates being forced to use software that we didn't choose, Current browser is MSN ie11.

https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox

Firefox is a web browser and Yahoo has been the default seach engine in en-US version of Firefox since 34.0.

Google is no longer the default search engine being used on the default homepage in Firefox which is about:home

https://blog.mozilla.org/blog/2014/11/19/promoting-choice-and-innovation-on-the-web/