In case your browser is using Yahoo as the default search engine, there are two possibilities. One is you installed an addon that changed your search engine to Yahoo. Another is your system may have the Yahoo search redirect virus. In this case, you should reset your browser settings.
You can change your search engine manually through the following steps:
Open the new tab.
Click on the three-dot menu in the right corner.
Click on settings.
Look for ‘setting’ in the left-hand side menu and click on it.
Now click on to manage the search engine option.
Click on the name of the search engine you want on your browser.