> 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/zh/web/xss/stored-dom-xss.md).
# XSS DOM 存储型
XSS DOM 存储型笔记，适用于 PortSwigger Web Security Academy 实验室，包括利用流程、载荷测试、Burp Suite 验证和修复上下文。
### 存储型 DOM XSS
本实验演示了博客评论功能中一个存储型 DOM 漏洞。要完成本实验，请利用此漏洞运行 `alert()` 函数。
如果你在评论区域插入经典的 `脚本` 到评论区域：
```javascript
```
我们注意到网站删除了评论的一部分。
该函数是：
```javascript
function loadComments(postCommentPath) {
let xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
let comments = JSON.parse(this.responseText);
displayComments(comments);
}
};
xhr.open("GET", postCommentPath + window.location.search);
xhr.send();
function escapeHTML(html) {
return html.replace('<', '<').replace('>', '>');
}
function displayComments(comments) {
let userComments = document.getElementById("user-comments");
for (let i = 0; i < comments.length; ++i)
{
comment = comments[i];
let commentSection = document.createElement("section");
commentSection.setAttribute("class", "comment");
let firstPElement = document.createElement("p");
let avatarImgElement = document.createElement("img");
avatarImgElement.setAttribute("class", "avatar");
avatarImgElement.setAttribute("src", comment.avatar ? escapeHTML(comment.avatar) : "/resources/images/avatarDefault.svg");
if (comment.author) {
if (comment.website) {
let websiteElement = document.createElement("a");
websiteElement.setAttribute("id", "author");
websiteElement.setAttribute("href", comment.website);
firstPElement.appendChild(websiteElement)
}
let newInnerHtml = firstPElement.innerHTML + escapeHTML(comment.author)
firstPElement.innerHTML = newInnerHtml
}
if (comment.date) {
let dateObj = new Date(comment.date)
let month = '' + (dateObj.getMonth() + 1);
let day = '' + dateObj.getDate();
let year = dateObj.getFullYear();
if (month.length < 2)
month = '0' + month;
if (day.length < 2)
day = '0' + day;
dateStr = [day, month, year].join('-');
let newInnerHtml = firstPElement.innerHTML + " | " + dateStr
firstPElement.innerHTML = newInnerHtml
}
firstPElement.appendChild(avatarImgElement);
commentSection.appendChild(firstPElement);
if (comment.body) {
let commentBodyPElement = document.createElement("p");
commentBodyPElement.innerHTML = escapeHTML(comment.body);
commentSection.appendChild(commentBodyPElement);
}
commentSection.appendChild(document.createElement("p"));
userComments.appendChild(commentSection);
}
}
};
```
* 该 `escapeHTML(HTML)` 函数不会转义 **第一个** 出现的 `<` 和 `>` (使用 `替换` 简单)。
* 由于代码随后使用 `innerHTML` 来插入值，恶意标签可能会保留并被浏览器解释。
* 因此，过滤仅对第一次出现有效；后续出现仍然存在漏洞。
* 使用全局替换（`replaceAll` 或全局正则表达式）来转义 **所有** 出现的 `<` 和 `>`.
* 避免将 `innerHTML` 用于不可靠数据；更推荐 `textContent` 或 `createTextNode`
可利用的载荷
* 闭合并注入脚本：
```javascript
<>
```
* 强制触发图片错误以触发 `onerror：`
```javascript
<>
```
这些载荷之所以有效，是因为只有少数字符被转换，而 `<`/`>` 的其他出现仍然可以被解析。
---
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