Seeks out things on the internet that are bad for them
Before You Begin
Pause and breathe. Even if this shouldn't be happening... accept that it is and embrace it with composure and calmness.
Calmness is the only way forward because without calm, there is no possibility for receptiveness and connection. Your child won't give to you any more than they see from you.
Never forget that a strong connection is fundamental, as there will be no correction in them if there is no connection with you.
The Core Problem
They get excitement from the inappropriate content, but don't understand that exposure to the content could dangerously desensitize them and/or distort their perception of reality.
What Will Make It Worse
Reacting with immediate anger or punishment might worsen the situation by increasing their interest in this content, and lead to them hiding the behavior.
Also, overly restricting internet access and/or not talking through the reasons this type of content is bad for them can be counterproductive as the child will most likely build resentment towards you and learn nothing.
What The Child Needs
1. Digital responsibility education: The child needs to understand the importance of responsible internet usage/internet self-governance based on the potential consequences (i.e. desensitization towards revolting actions, distortion of what is common/reality) that come from accessing inappropriate content. Emphasize the importance of seeking guidance if they come across something inappropriate or harmful that they didn't intent to see.
2. Clear boundaries: As soon as possible, establish clear guidelines of what inappropriate content is and what the punishment will be for seeking out, or not turning away from, such content.
3. Open communication with you: Encourage open and non-judgmental communication with your child, so they feel safe discussing any online experiences (even online multiplayer games) and seeking guidance when needed.
4. Guidance and supervision: Provide gentle guidance and supervision while using the internet, especially for younger children or those who struggle with self-regulation or seeing the distinction between appropriate and inappropriate content on their own.
How To Have The Conversation With Your Child
Find a distraction-free spot where the child feels comfortable talking.
Begin the conversation expressing understanding that the internet has nearly everything on it which makes make it very interesting; but for all of the good, there are many bad things that a child's curiosity might take them to.
Explain why it is so important to be responsible online, just like it is when they go play outside by themselves. Add that you know they are a good kid and you'd rather trust them to do the right thing versus taking away their internet access.
Next, talk through the provided "Digital responsibility education" pointer above, followed by setting the "Clear boundaries" (pointer 2).
End the conversation on pointer 3 with sincerity that you would rather have them share that they came across something that they shouldn't have seen, than keep it secret for fear of punishment.
The goal is for the child to come away from the conversation with more reason to avoid seeking out things on the internet that they know they shouldn't, ending that behavior, and more willing to be honest with you if they crossed a boundary (intentionally or not).