I'm not 100% sure of what's online, so apologies if I'm repeating what you've read:
This will only really resolve Safari side issues, but it's good to check, anyway. Make sure nothing dodgy shows up in Safari > Preferences > Extensions, and, in fact turn them off, quit Safari, and see if you're still having the issue.
You can also try checking Login items
If it's still showing up from there, try booting into Safe Mode (hold shift at the startup chime/first grey screen until you see the Apple logo). If the issues aren't showing up there, then we've got a non-Apple extension or startup item running normally. You can usually locate these in /Library/StartupItems, LaunchAgents and LaunchDaemons. You can safely remove anything that doesn't start with com.apple (or if you see com.genieo, there you go) from here - just put them off into a folder in the desktop or rename them with .old at the end. Reboot and test. It'll break some things at first, but just put some of the files back, until everything is working again, and you don't get Genieo issues.