Package Instance

Label Studio is an a popular open source data labeling tool. Versions prior to 1.9.2 have a cross-site scripting (XSS) vulnerability that could be exploited when an authenticated user uploads a crafted image file for their avatar that gets rendered as a HTML file on the website. Executing arbitrary JavaScript could result in an attacker performing malicious actions on Label Studio users if they visit the crafted avatar image. For an example, an attacker can craft a JavaScript payload that adds a new Django Super Administrator user if a Django administrator visits the image.

The file `users/functions.py` lines 18-49 show that the only verification check is that the file is an image by extracting the dimensions from the file. Label Studio serves avatar images using Django's built-in `serve` view, which is not secure for production use according to Django's documentation. The issue with the Django `serve` view is that it determines the `Content-Type` of the response by the file extension in the URL path. Therefore, an attacker can upload an image that contains malicious HTML code and name the file with a `.html` extension to be rendered as a HTML page. The only file extension validation is performed on the client-side, which can be easily bypassed.

Version 1.9.2 fixes this issue. Other remediation strategies include validating the file extension on the server side, not in client-side code; removing the use of Django's `serve` view and implement a secure controller for viewing uploaded avatar images; saving file content in the database rather than on the filesystem to mitigate against other file related vulnerabilities; and avoiding trusting user controlled inputs.

### Summary
On all Label Studio versions prior to 1.11.0, data imported via file upload feature is not properly sanitized prior to being rendered within a [`Choices`](https://labelstud.io/tags/choices) or [`Labels`](https://labelstud.io/tags/labels) tag, resulting in an XSS vulnerability.

### Details
Need permission to use the "data import" function. This was reproduced on Label Studio 1.10.1.

### PoC

1. Create a project.
![Create a project](https://github.com/HumanSignal/label-studio/assets/3943358/9b1536ad-feac-4238-a1bd-ca9b1b798673)

2. Upload a file containing the payload using the "Upload Files" function.
![2  Upload a file containing the payload using the Upload Files function](https://github.com/HumanSignal/label-studio/assets/3943358/26bb7af1-1cd2-408f-9adf-61e31a5b7328)
![3  complete](https://github.com/HumanSignal/label-studio/assets/3943358/f2f62774-1fa6-4456-9e6f-8fa1ca0a2d2e)

The following are the contents of the files used in the PoC
```
{
  "data": {
    "prompt": "labelstudio universe image",
    "images": [
      {
        "value": "id123#0",
        "style": "margin: 5px",
        "html": "<img width='400' src='https://labelstud.io/_astro/images-tab.64279c16_ZaBSvC.avif' onload=alert(document.cookie)>"
      }
    ]
  }
}
```

3. Select the text-to-image generation labeling template of Ranking and scoring
![3  Select the text-to-image generation labelling template for Ranking and scoring](https://github.com/HumanSignal/label-studio/assets/3943358/f227f49c-a718-4738-bc2a-807da4f97155)
![5  save](https://github.com/HumanSignal/label-studio/assets/3943358/9b529f8a-8e99-4bb0-bdf6-bb7a95c9b75d)

4. Select a task
![4  Select a task](https://github.com/HumanSignal/label-studio/assets/3943358/71856b7a-2b1f-44ea-99ab-fc48bc20caa7)

5. Check that the script is running
![5  Check that the script is running](https://github.com/HumanSignal/label-studio/assets/3943358/e396ae7b-a591-4db7-afe9-5bab30b48cb9)

### Impact
Malicious scripts can be injected into the code, and when linked with vulnerabilities such as CSRF, it can cause even greater damage. In particular, It can become a source of further attacks, especially when linked to social engineering.

Label Studio, an open source data labeling tool had a remote import feature allowed users to import data from a remote web source, that was downloaded and could be viewed on the website. Prior to version 1.10.1, this feature could had been abused to download a HTML file that executed malicious JavaScript code in the context of the Label Studio website. Executing arbitrary JavaScript could result in an attacker performing malicious actions on Label Studio users if they visit the crafted avatar image. For an example, an attacker can craft a JavaScript payload that adds a new Django Super Administrator user if a Django administrator visits the image.

`data_import/uploader.py` lines 125C5 through 146 showed that if a URL passed the server side request forgery verification checks, the contents of the file would be downloaded using the filename in the URL. The downloaded file path could then be retrieved by sending a request to `/api/projects/{project_id}/file-uploads?ids=[{download_id}]` where `{project_id}` was the ID of the project and `{download_id}` was the ID of the downloaded file. Once the downloaded file path was retrieved by the previous API endpoint, `data_import/api.py`lines 595C1 through 616C62 demonstrated that the `Content-Type` of the response was determined by the file extension, since `mimetypes.guess_type` guesses the `Content-Type` based on the file extension. Since the `Content-Type` was determined by the file extension of the downloaded file, an attacker could import in a `.html` file that would execute JavaScript when visited.

Version 1.10.1 contains a patch for this issue. Other remediation strategies are also available. For all user provided files that are downloaded by Label Studio, set the `Content-Security-Policy: sandbox;` response header when viewed on the site. The `sandbox` directive restricts a page's actions to prevent popups, execution of plugins and scripts and enforces a `same-origin` policy. Alternatively, restrict the allowed file extensions that may be downloaded.