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.
npx agentmods add skills/googlechrome/modern-web-guidance-src/securitynpx skills add GoogleChrome/modern-web-guidance-src --skill securitygit clone --depth 1 https://github.com/GoogleChrome/modern-web-guidance-srcWrote 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.
[](https://agentmods.dev/skills/googlechrome/modern-web-guidance-src/security)<a href="https://agentmods.dev/skills/googlechrome/modern-web-guidance-src/security"><img src="https://agentmods.dev/badge/skills/googlechrome/modern-web-guidance-src/security.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00040 | $0.05885 |
| Opus 5 | $0.00020 | $0.02942 |
| Sonnet 5 | $0.00008 | $0.01177 |
| Haiku 4.5 | $0.00004 | $0.00588 |
Grade A, and why
web-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 4d 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.
How it starts
The opening of the file, as written. The whole thing — 356 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Web Security
Guidelines for implementing preventative security measures on the web safely and incrementally.
NOTE: This skill covers standard web platform defenses, focusing mostly on the browser. Applications still require comprehensive server-side security, authorization models, and input validation.
Table of Contents
- When to apply this skill
- Phase 1: Quick Wins & Obvious Anti-Patterns
- 1.1 Secure Contexts
- 1.2 Avoid Dangerous DOM Sinks
- 1.3 Secure Cookies
- 1.4 Clickjacking Protection (Frame-Ancestors & X-Frame-Options)
- 1.5 Secure Window Messaging (postMessage)
- Phase 2: Discovery & Data Collection (Prerequisites)
- 2.1 Inspect the Application
- 2.2 Deploy Report-Only Policies
- 2.3 Data Hygiene for Reports
- 2.4 Automated Discovery via Browser APIs and DevTools
- Phase 3: Interpreting Results & Enforcement
- Core enforcement (data-driven rollouts)
- 3.1 Analyzing CSP Reports
- 3.2 Transitioning to CSP Enforcement
- 3.3 Trusted Types Enforcement
- 3.4 Cross-Origin Opener Policy (COOP)
- 3.5 Cross-Origin Resource Policy (CORP)
- 3.6 Cross-Origin Isolation
- 3.7 Fetch Metadata (Resource Isolation)
- Companion policies (deploy in parallel)
- HTTP Strict Transport Security (HSTS)
- X-Content-Type-Options
- Referrer Policy
- Permissions Policy
- Subresource Integrity (SRI)
- Cross-Origin Resource Sharing (CORS)
- Clear-Site-Data (Logout)
- Core enforcement (data-driven rollouts)
When to apply this skill
The right starting point depends on the application:
- Retrofitting an existing app: Always start at Phase 1. Strict policies applied without discovery will break the app. Treat Phase 2 (report-only) as a prerequisite for any Phase 3 enforcement.
- Greenfield app or new feature: You can adopt Phase 3 enforced policies directly, but still wire up reporting from day one.
- SaaS template / framework defaults: Ship Phase 1 hygiene and Phase 3 policies enabled by default, with Phase 2 reporting on so downstream users can detect regressions.
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.
- 4d ago First seen · 356 lines · 40 tokens per session scan A c0a82a5fb205
web-security is a skill published in the GitHub repository GoogleChrome/modern-web-guidance-src (1,002 stars, last pushed 4d ago), licensed Apache-2.0. It adds 40 tokens to every session and 5,885 once invoked, about $0.0002 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.
Other skills, from other repositories
systematic-debugging
Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.
brainstorming
You MUST use this before any creative work - creating features, building components, adding functionality, or modifying behavior. Explores user intent, requirements and design before implementation.
auto-perf-optimize
Run agent-driven VS Code performance or memory investigations. Use when asked to launch Code OSS, automate a VS Code scenario, run the Chat memory smoke runner, capture renderer heap snapshots, take workflow screenshots, compare run summaries, or drive a repeatable scenario before heap-snapshot analysis.
chat-perf
Run chat perf benchmarks and memory leak checks against the local dev build or any published VS Code version. Use when investigating chat rendering regressions, validating perf-sensitive changes to chat UI, or checking for memory leaks in the chat response pipeline.
chat-pet-sprite-creation
Use when creating or changing VS Code chat pet sprite art, sprite sheets, state animations, eye treatments, Stable/Insiders variants, or pet transitions under src/vs/workbench/contrib/chat/browser/widget/media/chatPet.
cpu-profile-analysis
Analyze V8/Chrome CPU profiles (.cpuprofile) and DevTools trace files (Trace-.json). Use when: profiling performance, investigating slow functions, comparing code paths, finding bottlenecks, analyzing timeToRequest, understanding call trees from sampling profiler data, analyzing layout/paint/rendering, investigating…