I have been infected by informationvine. Do you have a cleaner to get rid of it?

If the above doesn't work, go to Safari Preferences/Extensions and turn all extensions off. Quit/reopen Safari and test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

Check Safari/Preferences/General and reset your Homepage if necessary.

You can also try try Safari/Clear History…. 

Download and run Malwarebytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac.