PT-2026-59545 — Pypi Praisonai

PT-2026-59545 · Pypi · Praisonai

Published

2026-07-13

Updated

2026-07-13

CVSS v3.1

5.4

Medium

Vector

AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

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

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

Verify nh3 is not installed (default):

bash

pip show nh3 2>&1 | grep -c "not found"
# Returns 1 (not installed)

Start the API:

bash

python src/praisonai/api.py

Access the endpoint:

bash

curl http://localhost:5000/

Response contains unsanitized HTML:

html

<html><body><p><img src=x onerror=alert(document.cookie)></p></body></html>

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 fake login forms or exfiltrate data to attacker-controlled servers.
Actions on behalf of users: Malicious JavaScript can perform actions in the context of the victim's browser session.

The attack surface includes any scenario where agent output contains attacker-influenced content: RAG retrieval from poisoned documents, web scraping of malicious pages, processing of adversarial user prompts, or multi-agent communication where one agent's output is tainted.

Recommended Fix

Make nh3 a required dependency when using the API, and remove the silent fallback:

python

# Option 1: Make nh3 required in pyproject.toml under the "api" optional dependency
# In pyproject.toml:
# api = [
#   "flask>=3.0.0",
#   ...
#   "nh3>=0.2.14",
# ]

# Option 2: Use markdown's built-in HTML stripping as a safe default
import markdown

def sanitize html(html: str) -> str:
  try:
    import nh3
    return nh3.clean(html)
  except ImportError:
    import re
    return re.sub(r'<[^>]+>', '', html) # Strip all HTML tags as fallback

# Option 3 (preferred): Use Flask's Jinja2 templating with auto-escaping
# instead of f-string interpolation, or use markupsafe.escape()
from markupsafe import Markup

@app.route('/')
def home():
  output = basic()
  # Use markdown with safe extensions only
  html output = markdown.markdown(str(output), extensions=[])
  try:
    import nh3
    html output = nh3.clean(html output)
  except ImportError:
    raise RuntimeError("nh3 is required for safe HTML rendering. Install with: pip install nh3")
  return f'<html><body>{html output}</body></html>'

Also fix deploy.py:76-91 to include sanitization in the generated api.py.

Fix

Found an issue in the description? Have something to add? Feel free to write us 👾

dbugs@ptsecurity.com

Related Identifiers

PYSEC-2026-2910

Affected Products

Praisonai