DOM-Based XSS
Last updated
Last updated
The Document Object Model (DOM) presents an interesting problem from a security standpoint.
It allows the content of a web page to be dynamically modified, but that can abused by attackers during a malicious code injection.
XSS is a type of malicious code injection that can occur when unvalidated user input is used directly to modify the content of a page on the client side
Solution:
Inspect element of the text field input
We can see that input field is using a JavaScript function named displayGreeting, which is listed in the script tag above.
Navigate to that link to see the JS source code.
Here we see…
function displayGreeting(name) {
if (name != ''){
document.getElementById("greeting").innerHTML="Hello, " + name+ "!";
}
}
The user is inputing directly into the JS code.
Because of this, the user can simply type " in the input field to close the string and then insert malicious JavaScript code directly onto the server.
In this case, we are inserting a .jpg file onto the webpage.
e.g. we will enter..
"<IMG src=images/logos/owasp.jpg>
Into the form field
