You may need to reset a preference if "Search Results" or "My Search Results" is appearing as a search engine every time you open a new tab (follow steps 1-4 below the image to determine what opens when you click to open a new tab; see about:config usage above) - https://support.mozilla.org/en-US/kb/new-tab-page-show-hide-and-customize-top-sites#w_how-do-i-turn-the-new-tab-page-off
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