If you are getting notifications from OperativeIndexer, then your Mac is infected with adware. OperativeIndexer is adware for Mac.
OperativeIndexer changes setting in your Mac. First, OperativeIndexer installs a browser extension in your browser. Then, after OperativeIndexer 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.