No-young children have very little understanding of being safe on the internet. they could share your personal information with strangers and/or be victims of scam. sometimes children can get immature and search unpleasant things on the internet, or they could innocently come across something inappropriate. to prevent this type of thing from happening, you should:
password protect your computer so only you could access it
supervise the kid on the internet at all
block certain websites to make them impossible to view
teach them what to do when they encounter spam messages etc.