HTML Injection happens when a website takes user input and displays it on the page without filtering or sanitizing it first.

This allows attackers to insert their own HTML code into the webpage.

Simple Idea

The website expects:

Emmanuel

But instead, the attacker submits:

<h1>Hacked</h1>

If the application blindly displays the input, the browser interprets it as real HTML instead of plain text.

So the page changes.

Why This Is Dangerous

HTML Injection may seem harmless at first, but it can lead to serious attacks.

1. Fake Login Forms (Phishing)

2. Website Defacement

3. Malicious Advertisements

4. Stepping Stone to XSS e.g

Site expects:

<input value="USER_INPUT">