headless-browser

An autonomous helper for testing web applications for security weaknesses through a browser that runs without a visible window. It uses an MCP-connected toolkit to navigate web pages.

In plain words
What is it for?
Navigating a web application during a penetration test and using browser interactions to investigate possible security issues.
Why use it?
It can carry out browser-based security testing without requiring someone to click through every page manually.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/ascit31/dark-moon/headless-browser
Clone the repo
git clone --depth 1 https://github.com/ASCIT31/Dark-Moon
Per session 24 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 8,101 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 findings. Scan, not verified.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00024 $0.08101
Opus 5 $0.00012 $0.04050
Sonnet 5 $0.00005 $0.01620
Haiku 4.5 $0.00002 $0.00810

Measured 2d ago against content hash 56dc1fdc0d29, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

headless-browser scanned grade A with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- curl

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

- You DO NOT use child_process
conf/agents/headless-browser.md · 882 lines

The source is not reproduced here

Licensed GPL-3.0

The repository is licensed GPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 882 lines · 24 tokens per session scan A 56dc1fdc0d29

Subscribe to this mod's changes

headless-browser is an agent published in the GitHub repository ASCIT31/Dark-Moon (886 stars, last pushed 4d ago), licensed GPL-3.0. It adds 24 tokens to every session and 8,101 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.