This attack is really similar to to Cross-Site Scripting attacks.
What we can do:
- Create a fake login-page, that tricks the user to log in again, but the post-is sent to a server that the attacker controls. And can thereby steal the credentials of the user.
- Inject javacript.
The attacker can inject html forms that tricks the user into giving up sensitive data.
See eventhandlers for more ways: https://www.owasp.org/index.php/XSS\_Filter\_Evasion\_Cheat\_Sheet\#Event\_Handlers
<IMG SRC=# onmouseover="alert('xxs')">