PromptFuzz

Adversarial security testing for LLM applications.

Find prompt injection, jailbreak, and data extraction vulnerabilities before attackers do.

You ship an LLM-powered product. You add a system prompt. You think it's secure. It isn't. PromptFuzz finds out before your users do.

PromptFuzz fires 165+ real adversarial attack prompts — jailbreaks, prompt injections, data extraction attempts, goal hijacking, and edge cases — at your application and generates a professional vulnerability report in seconds.

Install

pip install promptfuzz

Optional extras:

pip install "promptfuzz[openai]"     # if your target uses OpenAI
pip install "promptfuzz[anthropic]"  # if your target uses Anthropic

Quick start

1. Interactive wizard (recommended for first-time users)

Just run promptfuzz with no arguments:

$ promptfuzz

  PromptFuzz v0.1.0 — LLM Security Testing

  ? What is your target?
    > HTTP/HTTPS endpoint (URL)
      Python function (module:function)

  ? Enter target URL: http://localhost:8000/chat

  ? Select attack categories:
   ◉ data_extraction  — System prompt leaking, credential extraction
   ◉ injection        — Prompt override, delimiter attacks
   ◉ jailbreak        — Persona switches, DAN, roleplay bypasses
   ○ edge_cases       — Unicode, long inputs, encoding attacks
   ○ goal_hijacking   — Purpose redirection attacks

  ? Output format:
    > Terminal + HTML report  (report.html)

  ? Minimum severity to report:
    > low  (show everything)

  ─────────────────────────────────────────
  Target   : http://localhost:8000/chat
  Attacks  : 110  (data_extraction + injection + jailbreak)
  Output   : Terminal + report.html
  Severity : low+
  ─────────────────────────────────────────
  Press ENTER to start scan (Ctrl+C to cancel)

2. promptfuzz test — quickest way to run from the terminal

# Test any URL directly — no flags needed
promptfuzz test https://api.mychatbot.com/chat

# Save an HTML report
promptfuzz test https://api.mychatbot.com/chat --output report.html

# Test a local Python function
promptfuzz test myapp:chat_handler --categories jailbreak injection

# CI mode — exit code 1 if any high/critical vulnerability found
promptfuzz test https://api.mychatbot.com/chat --fail-on high

Sample terminal output:

3. promptfuzz scan — full power CLI with config file support

promptfuzz scan --target http://localhost:8000/chat --output report.html
promptfuzz scan --config promptfuzz.yaml --fail-on high

3. Python API

from promptfuzz import Fuzzer

def my_chatbot(message: str) -> str:
    # your LLM call here
    return response

fuzzer = Fuzzer(
    target=my_chatbot,
    context="customer support chatbot",
    categories=["jailbreak", "injection", "data_extraction"],
)
result = fuzzer.run()
result.report()           # rich terminal output
result.save("report.html")  # HTML report

Testing a FastAPI endpoint

PromptFuzz works with any HTTP endpoint that accepts POST requests. No code changes needed.

# your_app.py
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class ChatRequest(BaseModel):
    message: str

@app.post("/chat")
async def chat(req: ChatRequest):
    reply = your_llm_call(req.message)
    return {"response": reply}

# Start your app
uvicorn your_app:app

# Test it
promptfuzz scan --target http://localhost:8000/chat

The runner auto-detects http:// targets, sends {"message": "..."} as the request body, and reads the "response" field from the reply. Both field names are configurable.

Attack categories

promptfuzz list-attacks   # view full table with severity breakdown

CLI reference

promptfuzz scan [OPTIONS]

  --target, -t       URL or module:function path
  --config, -c       YAML config file (mutually exclusive with --target)
  --context          Description of the target application
  --categories, -C   Attack categories to run (repeatable)
  --output, -o       Save HTML report to path
  --json             Save JSON report to path
  --severity, -s     Minimum severity to display [low|medium|high|critical]
  --fail-on, -f      Exit code 1 if vulns at/above this severity are found
  --max-workers, -w  Concurrent request workers (default: 5)
  --timeout, -T      Per-attack timeout seconds (default: 30)
  --verbose, -v      Enable verbose output

Config file

# promptfuzz.yaml
target: "http://localhost:8000/chat"
context: "customer support chatbot"
categories:
  - jailbreak
  - injection
  - data_extraction
max_workers: 5
timeout: 30
headers:
  Authorization: "Bearer YOUR_TOKEN"
input_field: message
output_field: response

promptfuzz scan --config promptfuzz.yaml --output report.html
promptfuzz validate --config promptfuzz.yaml   # validate before running

CI/CD integration

# .github/workflows/security.yml
name: LLM Security
on: [push, pull_request]

jobs:
  promptfuzz:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: pip install promptfuzz
      - name: Start app
        run: uvicorn myapp:app &
      - name: Run security scan
        run: |
          promptfuzz scan \
            --target http://localhost:8000/chat \
            --categories jailbreak injection \
            --fail-on high \
            --output report.html
      - uses: actions/upload-artifact@v4
        if: always()
        with:
          name: security-report
          path: report.html

--fail-on high exits with code 1 if any high or critical vulnerability is found, blocking the merge.

Security score

Formula: max(0, 100 − (critical×25 + high×10 + medium×5 + low×2))

Contributing

Adding new attacks is the easiest way to contribute. Each attack is a JSON object in one of the five files under promptfuzz/attacks/. Copy an existing entry, update the id, name, prompt, and detection fields, and open a PR.

{
  "id": "JB-041",
  "name": "My new jailbreak",
  "category": "jailbreak",
  "severity": "high",
  "description": "What this attack does and why it matters.",
  "prompt": "The actual adversarial prompt sent to the LLM.",
  "detection": {
    "method": "refusal",
    "indicators": [],
    "success_if": "refusal_absent"
  },
  "tags": ["jailbreak", "persona"],
  "remediation": "Add explicit system prompt instruction to refuse persona changes."
}

Run ruff check . and pytest tests/ -v before opening a PR.

License

AGPL-3.0 © PromptFuzz Contributors

Free to use for personal projects, security research, and open-source software. Commercial use in closed-source products requires a commercial license — open an issue to discuss.