This has been an ongoing problem for me as well. What can I do to prevent this.

I have a Mac and the Firefox version I use is 59.0.2

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.

Also remove SafeSearch, SearchAssist Incognito, FileConverter Addon, SearchLock, DiscreteSearch, WebSearch, Findwide Search Engine

Now do the same in the computer’s Programs Folder.

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

Hi, you can also check that malware from Search Assist is also removed : https://www.malwarebytes.com/mac/

I don't know if this holds true for all operating systems or all localizations, but as of Firefox 58 the Yahoo search engine is gone from my Firefox installation. The "deal" that Mozilla had with Yahoo for search engine placement in Firefox (and as the "default") ended when Yahoo was sold. So, both of you have "something" installed which has taken over your search functionality in Firefox.

FredMcD said

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. Also remove SafeSearch, SearchAssist Incognito, FileConverter Addon, SearchLock, DiscreteSearch, WebSearch, Findwide Search Engine Now do the same in the computer’s Programs Folder. Windows: Start > Control Panel > Uninstall Programs. Mac: Open the Applications folder. Linux: Check your user manual.

Thanks for helping, unfortunately though, both of these places were squeaky clean. That being said, it hasn't switched back to yahoo since I originally posted so perhaps I will wait and see if it happens again...

SaltyLimes said

FredMcD said

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. Also remove SafeSearch, SearchAssist Incognito, FileConverter Addon, SearchLock, DiscreteSearch, WebSearch, Findwide Search Engine Now do the same in the computer’s Programs Folder. Windows: Start > Control Panel > Uninstall Programs. Mac: Open the Applications folder. Linux: Check your user manual.

Thanks for helping, unfortunately though, both of these places were squeaky clean. That being said, it hasn't switched back to yahoo since I originally posted so perhaps I will wait and see if it happens again...

So it just switched back to Yahoo! So frustrating, any other ideas?

SaltyLimes said

So it just switched back to Yahoo! So frustrating, any other ideas?

Was this after a system restart, or a Firefox update, or any other potentially triggering event?

What is the exact name of the search plugin on the Preferences page? For example, Yahoo!, Yahoo! Search, etc. This article points the way to that panel, although probably you are quite familiar with it already: Change your default search settings in Firefox.

What is the URL of the results page when you search using that plugin? Sometimes the URL includes "affiliate" parameters that can link it to a particular source.

Do you use any "cleaning" software that may touch or roll back files in your Firefox profile (settings) folder?