Even when you are sure that you didn't install anything you still should be looking out at your Extensions. Lets go step by step in solving your Malware and Spammy Links in Google Chrome
Chrome Cleanup Tool searches your computer for suspicious programs and offers to remove them for you. On your Windows computer, visit the Chrome Cleanup Tool website.
You can try MalwareBytes, an anti-malware program that can find other malicious software that the Chrome Cleanup Tool might not remove.