looking up things on the internet shows search.yahoo not firefox

https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox Firefox is a web browser only and not a search engine. A search engine is for example qwant.com, duckduckgo.com, google.com, bing.com The desktop Firefox has not come with a Yahoo search engine as a default option since the Firefox 57.0 Release. So perhaps an extension you have installed or updated recently add this yahoo search engine.