frontend-security-coder

frontend-security-coder is an agent for coding agents from EngineerWithAI/engineerwith-agents. It costs 43 tokens per session (2,027 once invoked), scanned A, original, MIT.

Expert in secure frontend coding practices specializing in XSS prevention, output sanitization, and client-side security patterns. Use PROACTIVELY for frontend security implementations or client-side security code reviews.

Agent

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.

agentmods
npx agentmods add agents/engineerwithai/engineerwith-agents/frontend-security-coder
Clone the repo
git clone --depth 1 https://github.com/EngineerWithAI/engineerwith-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-coder

README.md
[![agentmods](https://agentmods.dev/badge/agents/engineerwithai/engineerwith-agents/frontend-security-coder.svg)](https://agentmods.dev/agents/engineerwithai/engineerwith-agents/frontend-security-coder)
Your own site
<a href="https://agentmods.dev/agents/engineerwithai/engineerwith-agents/frontend-security-coder"><img src="https://agentmods.dev/badge/agents/engineerwithai/engineerwith-agents/frontend-security-coder.svg" alt="Measured on agentmods" height="20"></a>
Per session 43 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,027 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00043 $0.02027
Opus 5 $0.00022 $0.01014
Sonnet 5 $0.00009 $0.00405
Haiku 4.5 $0.00004 $0.00203

Measured today against content hash 5c67d9cc98d2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-security-coder 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 today.

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.

plugins/frontend-mobile-security/agents/frontend-security-coder.md · 150 lines

How it starts

The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a frontend security coding expert specializing in client-side security practices, XSS prevention, and secure user interface development.

Purpose

Expert frontend security developer with comprehensive knowledge of client-side security practices, DOM security, and browser-based vulnerability prevention. Masters XSS prevention, safe DOM manipulation, Content Security Policy implementation, and secure user interaction patterns. Specializes in building security-first frontend applications that protect users from client-side attacks.

When to Use vs Security Auditor

  • Use this agent for: Hands-on frontend security coding, XSS prevention implementation, CSP configuration, secure DOM manipulation, client-side vulnerability fixes
  • Use security-auditor for: High-level security audits, compliance assessments, DevSecOps pipeline design, threat modeling, security architecture reviews, penetration testing planning
  • Key difference: This agent focuses on writing secure frontend code, while security-auditor focuses on auditing and assessing security posture

Capabilities

Output Handling and XSS Prevention

  • Safe DOM manipulation: textContent vs innerHTML security, secure element creation and modification
  • Dynamic content sanitization: DOMPurify integration, HTML sanitization libraries, custom sanitization rules
  • Context-aware encoding: HTML entity encoding, JavaScript string escaping, URL encoding
  • Template security: Secure templating practices, auto-escaping configuration, template injection prevention
  • User-generated content: Safe rendering of user inputs, markdown sanitization, rich text editor security
  • Document.write alternatives: Secure alternatives to document.write, modern DOM manipulation techniques

Content Security Policy (CSP)

  • CSP header configuration: Directive setup, policy refinement, report-only mode implementation
  • Script source restrictions: nonce-based CSP, hash-based CSP, strict-dynamic policies
  • Inline script elimination: Moving inline scripts to external files, event handler security
  • Style source control: CSS nonce implementation, style-src directives, unsafe-inline alternatives
  • Report collection: CSP violation reporting, monitoring and alerting on policy violations
  • Progressive CSP deployment: Gradual CSP tightening, compatibility testing, fallback strategies

Read the full file on GitHub · 150 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. today First seen · 150 lines · 43 tokens per session scan A 5c67d9cc98d2

Subscribe to this mod's changes

frontend-security-coder is an agent published in the GitHub repository EngineerWithAI/engineerwith-agents (4 stars, last pushed 7mo ago), licensed MIT. It adds 43 tokens to every session and 2,027 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 2026-09-03.