re-browser-ext

re-browser-ext is a skill for Claude Code from dslsdzc/rev-skills. It costs 59 tokens per session (2,724 once invoked), scanned A, original, Apache-2.0.

A workflow for examining browser extensions, which are add-ons packaged as CRX, XPI, or ZIP files for browsers such as Chrome and Firefox.

In plain words
What is it for?
Use it to unpack extensions, read their manifests and JavaScript, audit permissions, and safely test how they behave when loaded in a browser.
Why use it?
It provides an orderly way to inspect an extension’s files, permissions, scripts, and behavior, including signs of excessive access or harmful updates.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to unpack extensions, read their manifests and JavaScript, audit permissions, and safely test how they behave when loaded in a browser.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/dslsdzc/rev-skills/re-browser-ext
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 dslsdzc/rev-skills --skill re-browser-ext
Clone the repo
git clone --depth 1 https://github.com/dslsdzc/rev-skills

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 re-browser-ext

README.md
[![agentmods](https://agentmods.dev/badge/skills/dslsdzc/rev-skills/re-browser-ext/github.svg)](https://agentmods.dev/skills/dslsdzc/rev-skills/re-browser-ext)
Your own site
<a href="https://agentmods.dev/skills/dslsdzc/rev-skills/re-browser-ext"><img src="https://agentmods.dev/badge/skills/dslsdzc/rev-skills/re-browser-ext/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 re-browser-ext

Your own site · 80×15
<a href="https://agentmods.dev/skills/dslsdzc/rev-skills/re-browser-ext"><img src="https://agentmods.dev/badge/skills/dslsdzc/rev-skills/re-browser-ext.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 59 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,724 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 pass 7 Sept 2026
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 $0.00059 $0.02724
Opus 5 $0.00030 $0.01362
Sonnet 5 $0.00012 $0.00545
Haiku 4.5 $0.00006 $0.00272

Measured 9d ago against content hash 320a16368f28, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

re-browser-ext 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 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.

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.

.claude/skills/re-browser-ext/SKILL.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

浏览器扩展逆向

何时使用 / 何时不用

  • 用:扩展文件(crx/xpi/zip)、恶意扩展行为分析、扩展权限审计
  • 用:判断扩展是否过度授权、远程代码、更新投毒(首版干净后续版本恶意)
  • 不用:网页 JS 混淆([[re-script-deob]] 覆盖纯脚本)
  • 不用:Chrome/Edge 浏览器本身的漏洞利用(扩展与浏览器漏洞是两个对象)
  • 注意:动态加载扩展跑恶意行为属执行未知代码——沙箱内进行([[re-sandbox]],[[platform-tips]] 最高原则)

工具准备

unzip / 7z / python zipfile(解包)

  • 安装与验证见 [[re-doc-malware]] 工具准备(7z)
  • crx = "Cr24" 头(版本号 + 头长度;crx2 含公钥与签名、crx3 含 protobuf 头与 proof)+ 尾部 zip 数据——unzip/7z 直接解包会报 extra bytes at beginning 警告但结果正确;python3 -m zipfile -e sample.crx ext/ 无警告
  • xpi 就是纯 zip,直接解

jq(manifest 解析)

  • Linux: apt install jq;macOS: brew install jq;Windows: 官方构建
  • 验证: jq --version

node / js-beautify(脚本还原)

  • Linux: apt install nodejs;macOS: brew install node;Windows: nodejs.org 官方安装包;验证: node --version
  • js-beautify: npm install -g js-beautify,验证 js-beautify --version(压缩 JS 先格式化再读)

浏览器加载验证(动态,沙箱)

  • Chromium 系: chrome://extensions 开发者模式 → Load unpacked;Edge 同(edge://extensions
  • Firefox: about:debugging#/runtime/this-firefox → Load Temporary Add-on(免签名临时加载)
  • 验证: 扩展出现在扩展列表、后台脚本/页面能打开

操作步骤

按顺序执行,每步产物存档(路径 + sha256,见 [[re-triage]])。

  1. 解包与结构

    unzip -o sample.crx -d ext/ 2>/dev/null || python3 -m zipfile -e sample.crx ext/
    jq '.manifest_version, .name, .version' ext/manifest.json
    jq '.permissions, .host_permissions' ext/manifest.json
    # host_permissions 为 MV3 字段;MV2 站点权限在 permissions 内(含 URL 匹配模式)
    
    • 结构:manifest.json + 背景脚本(MV3 service worker / MV2 background page)+ 内容脚本(content_scripts)+ 页面(options/popup)+ 资源(web_accessible_resources)
    • 先确认 manifest_version(2 还是 3)——MV2/MV3 的权限模型与能力差异决定后续所有判断(见 [[gotchas]])
    • 其他关键字段:update_url(自托管更新清单,投毒面)、key(扩展 ID 派生)、externally_connectable(外部页面消息通道)、oauth2(令牌)、optional_permissions(运行时再要权)、minimum_chrome_version(兼容边界)
    • 次要结构:_locales/(i18n 消息,可藏字符串)、icons/options_page / options_uicommands(快捷键,触发行为入口)、incognito(隐身窗口行为声明)
  2. 权限审计(能力边界)

    • 高危 API 权限:tabs(读标签页 URL/标题)、storage(数据收集缓存)、webRequest(流量观察;MV3 阻断能力仅企业策略部署例外,一般改走 declarativeNetRequest)、scripting(MV3 动态注入)、clipboardRead(剪贴板)、cookies(读站点 Cookie)、historydownloadsnativeMessaging(与宿主程序通信)、debugger
    • 站点权限(host_permissions / MV2 permissions 内 URL 模式)决定能碰哪些网站的数据——<all_urls>*://*/* 是高危信号
    • 权限与声明用途对照:装了 storage+tabs+<all_urls> 但功能只是改主题——越权信号
    • 权限风险速查(声明即能力,不必看代码):

Read the full file on GitHub · 119 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 119 lines · 59 tokens per session scan A 320a16368f28

Subscribe to this mod's changes

re-browser-ext is a skill published in the GitHub repository dslsdzc/rev-skills (50 stars, last pushed 11d ago), licensed Apache-2.0. It adds 59 tokens to every session and 2,724 once invoked, about $0.0003 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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