Had this issue where my search engines were changed to the Yahoo related Safe Finder / Safer Find. Malwarebytes got rid of a bunch of related things, but my Safari new window kept defaulting to search.safefinderformac.com, despite changing it manually in Preferences. I manually dug through ~/Library/Safari/Bookmarks.plist, first via TextEdit, and found the SafeFind entry, finally. I then downloaded PlistEdit Pro from https://www.fatcatsoftware.com/plisteditpro/, searched the entry there, found it again, and removed the entire entry, beginning with the number. I also removed all Flash related installers, and entries I couldn't identify in Users/Shared.