GitHub Security Advisory: GHSA-cfg2-mxfj-j6pw
Package: PraisonAI (PIP)
Severity: MODERATE (CVSS 5.4)
CWE: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Vulnerable versions: < 4.5.128
Patched in: 4.5.128

Summary: PraisonAI Vulnerable to Stored XSS via Unsanitized Agent Output in HTML Rendering (nh3 Not a Required Dependency)

Details:
## Summary

The Flask API endpoint in `src/praisonai/api.py` renders agent output as HTML without effective sanitization. The `_sanitize_html` function relies on the `nh3` library, which is not listed as a required or optional dependency in `pyproject.toml`. When `nh3` is absent (the default installation), the sanitizer is a no-op that returns HTML unchanged. An attacker who can influence agent input (via RAG data poisoning, web scraping results, or prompt injection) can inject arbitrary JavaScript that executes in the browser of anyone viewing the API output.

## Details

In `src/praisonai/api.py`, lines 6-14 define the sanitizer with a try/except ImportError fallback:

```python
try:
    import nh3
    def _sanitize_html(html: str) -> str:
        return nh3.clean(html)
except ImportError:
    def _sanitize_html(html: str) -> str:
        """Fallback: no nh3, return as-is (install nh3 for XSS protection)."""
        return html
```

The `home()` route at lines 21-25 converts agent output to HTML via `markdown.markdown()` (which preserves raw HTML tags by default) and embeds it in an HTML response using an f-string — bypassing Flask's Jinja2 auto-escaping:

```python
@app.route('/')
def home():
    output = basic()
    html_output = _sanitize_html(markdown.markdown(str(output)))
    return f'<html><body>{html_output}</body></html>'
```

Since `nh3` is not in any dependency list (`pyproject.toml` core deps, optional deps, or requirements files), a standard installation will always hit the fallback path. The `markdown` library's default behavior passes through raw HTML tags in input text, so any `<script>` or event handler attributes in the agent output flow directly into the response.

Additionally, `deploy.py:76-91` generates a deployment version of `api.py` that has **no sanitization at all** — it directly calls `markdown.markdown(output)` without any `_sanitize_html` wrapper.

## PoC

1. Set up a PraisonAI instance with an agent that processes external content (e.g., web scraping or RAG retrieval):

```yaml
# agents.yaml
framework: crewai
topic: test
roles:
  researcher:
    role: Researcher
    goal: Process user-provided content
    backstory: You process content exactly as given
    tasks:
      process:
        description: "Return this exact text: <img src=x onerror=alert(document.cookie)>"
        expected_output: The text as-is
```

2. Verify `nh3` is not installed (default):
```bash
pip show nh3 2>&1 | grep -c "not found"
# Returns 1 (not installed)
```

3. Start the API:
```bash
python src/praisonai/api.py
```

4. Access the endpoint:
```bash
curl http://localhost:5000/
```

5. Response contains unsanitized HTML:
```html
<html><body><p><img src=x onerror=alert(document.cookie)></p></body></html>
```

6. Opening this in a browser executes the JavaScript payload.

## Impact

- **Session hijacking**: An attacker can steal cookies or session tokens from users viewing the API output.
- **Credential theft**: Injected scripts can present fak