Safari Keeps Opening Unwanted Pages on Mac
Every time I use Safari it opens multiple unwanted pages of ads that look like they are from Apple Support and Adobe. The unwanted pages open whenever I follow a link or open another web page. I am using a 4 year old MacBook Air 1.7 GHz, 8 GB. Using Safari Version 11.0.3. How do I stop this? I don't want to download any software to fix this because there are so many risks involved in that. I've tried erasing all my Safari cookies and history - didn't help.
Thank you.
MacBook Air, macOS Sierra (10.12.6)