If you are getting notifications from MainFrameSelect, then your Mac is infected with adware. MainFrameSelect is adware for Mac.
MainFrameSelect changes setting in your Mac. First, MainFrameSelect installs a browser extension in your browser. Then, after MainFrameSelect hijacks your browser, it modifies settings in the browser. For example, it changes the default home page, modifies search results, and displays unwanted pop-ups in your browser.