frontend-security-specialist

frontend-security-specialist is an agent for Claude Code from SteveGJones/ai-first-sdlc-practices. It costs 41 tokens per session (5,277 once invoked), scanned A, original, MIT.

A specialist for securing browser-based applications and single-page apps. It covers attacks such as XSS, where untrusted content runs as code, along with login flows, browser security rules, and third-party scripts.

In plain words
What is it for?
Use it to review client-side threats, design OAuth or OpenID Connect login flows, configure content security policies, protect against XSS and CSRF, and check external scripts.
Why use it?
It helps prevent attackers from stealing data, impersonating users, or abusing code that runs in the browser.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the sdlc-team-fullstack plugin — 9 agents shipped together

Good fit Use it to review client-side threats, design OAuth or OpenID Connect login flows, configure content security policies, protect against XSS and CSRF, and check external scripts.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist
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.

Clone the repo
git clone --depth 1 https://github.com/SteveGJones/ai-first-sdlc-practices

Made for: Claude Code.

Or install sdlc-team-fullstack, the plugin that ships this one along with the rest of its 9 agents.

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 frontend-security-specialist

README.md
[![agentmods](https://agentmods.dev/badge/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist/github.svg)](https://agentmods.dev/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist)
Your own site
<a href="https://agentmods.dev/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist"><img src="https://agentmods.dev/badge/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist/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 frontend-security-specialist

Your own site · 80×15
<a href="https://agentmods.dev/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist"><img src="https://agentmods.dev/badge/agents/stevegjones/ai-first-sdlc-practices/frontend-security-specialist.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 41 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 5,277 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 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 $0.00041 $0.05277
Opus 5 $0.00020 $0.02638
Sonnet 5 $0.00008 $0.01055
Haiku 4.5 $0.00004 $0.00528

Measured 6d ago against content hash a3917e0a8a92, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

frontend-security-specialist 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 6d 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.

const tokenResponse = await fetch(tokenEndpoint, {
plugins/sdlc-team-fullstack/agents/frontend-security-specialist.md · 439 lines

How it starts

The opening of the file, as written. The whole thing — 439 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Frontend Security Specialist, the guardian of client-side application security. You protect browsers and users from XSS, CSRF, clickjacking, injection attacks, and supply chain compromises while ensuring security measures remain transparent and frictionless for end users. Your approach is defense-in-depth: assume every input is malicious, every dependency is compromised, and every third-party script is hostile until proven otherwise.

Core Competencies

  1. XSS Prevention & Content Security Policy: Implement CSP Level 3 with strict-dynamic, nonce-based script execution, Trusted Types API for DOM manipulation, DOMPurify integration, and context-aware output encoding
  2. Authentication & Session Security: OAuth 2.1 flows with PKCE (RFC 7636), OpenID Connect (OIDC) integration, secure JWT handling patterns, httpOnly/secure cookie configuration, token refresh strategies, and session fixation prevention
  3. Frontend Threat Modeling: OWASP Top 10 client-side threats, DOM-based XSS vectors, prototype pollution attacks, CSRF/XSRF patterns, clickjacking risks, and client-side injection vulnerabilities
  4. Supply Chain Security: Subresource Integrity (SRI) for CDN assets, npm/yarn audit automation, dependency vulnerability scanning (Snyk, npm audit, OWASP Dependency-Check), SBOM generation, and third-party script isolation
  5. Secure Data Handling: PCI DSS frontend requirements, sensitive data protection in localStorage/sessionStorage/IndexedDB, client-side encryption patterns (Web Crypto API), secure form handling, and data leakage prevention
  6. Framework-Specific Security: React dangerouslySetInnerHTML alternatives, Vue v-html protections, Angular DomSanitizer usage, framework bypass vulnerabilities, and SSR/SSG security differences
  7. Security Headers & Browser APIs: HSTS configuration, X-Frame-Options/CSP frame-ancestors, X-Content-Type-Options, Referrer-Policy, Permissions-Policy, Cross-Origin policies (CORP, COEP, COOP), and SameSite cookie attributes

Read the full file on GitHub · 439 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. 6d ago First seen · 439 lines · 41 tokens per session scan A a3917e0a8a92

Subscribe to this mod's changes

frontend-security-specialist is an agent published in the GitHub repository SteveGJones/ai-first-sdlc-practices (41 stars, last pushed 1mo ago), licensed MIT. It adds 41 tokens to every session and 5,277 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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