Frontend Security Coder
Harden client-side code with XSS-safe patterns, CSP, and secure DOM handling while you ship web UI.
Overview
frontend-security-coder is an agent skill most often used in Ship (also Build frontend) that implements secure client-side coding patterns including XSS prevention and CSP-oriented hardening.
Install
npx skills add https://github.com/sickn33/antigravity-awesome-skills --skill frontend-security-coderWhat is this skill?
- Hands-on XSS prevention and output sanitization patterns for real UI code
- Safe DOM manipulation and secure user-interaction guidance
- Content Security Policy (CSP) implementation orientation
- Contrasts implementation work vs read-only security auditor reviews
- Points to resources/implementation-playbook.md for deeper examples
Adoption & trust: 607 installs on skills.sh; 40.1k GitHub stars; 3/3 security scanners passed (skills.sh audits).
What problem does it solve?
You are shipping UI that handles untrusted input or dynamic HTML and need repeatable secure-coding patterns instead of ad-hoc fixes after a scare.
Who is it for?
Solo builders coding React, Vue, or vanilla SPAs who want security-first defaults while implementing features.
Skip if: Teams needing org-wide compliance attestations, backend-only auth design, or a passive audit with no code changes—use a dedicated security auditor skill or firm for that scope.
When should I use this skill?
Working on frontend security coder tasks or workflows, or needing XSS prevention, sanitization, and client-side security checklists.
What do I get? / Deliverables
You leave with actionable frontend security steps—sanitization, DOM-safe patterns, and CSP guidance—ready to verify in code and staging before wider release.
- Actionable secure-coding steps aligned to the current UI task
- Verification notes for XSS/CSP-related changes
Recommended Skills
Journey fit
Spans multiple journey phases - primary shelf plus alternate fits below.
Security hardening belongs on the Ship shelf because it gates release readiness for user-facing apps. Subphase security is where solo builders implement preventative controls before launch, not only after an audit.
Where it fits
Wire a comments feed with sanitization rules before rendering HTML from users.
Tighten CSP and inline-script policy ahead of a public beta launch.
Self-review a PR that touches innerHTML or dangerouslySetInnerHTML equivalents.
Patch a reported reflected XSS in a legacy marketing page without regressing UX.
How it compares
Implementation-focused secure frontend coding, not a read-only security audit report.
Common Questions / FAQ
Who is frontend-security-coder for?
Indie and solo developers shipping browser apps who want expert-level XSS, sanitization, and CSP guidance embedded in their coding workflow.
When should I use frontend-security-coder?
Use it while building or hardening UI in Build (frontend integrations) and again in Ship (security) before launch—especially when rendering user content, rich text, or third-party scripts.
Is frontend-security-coder safe to install?
It is community-sourced procedural knowledge; review the Security Audits panel on this Prism page and treat any external playbook files like normal project dependencies before trusting them in CI.
SKILL.md
READMESKILL.md - Frontend Security Coder
## Use this skill when - Working on frontend security coder tasks or workflows - Needing guidance, best practices, or checklists for frontend security coder ## Do not use this skill when - The task is unrelated to frontend security coder - You need a different domain or tool outside this scope ## Instructions - Clarify goals, constraints, and required inputs. - Apply relevant best practices and validate outcomes. - Provide actionable steps and verification. - If detailed examples are required, open `resources/implementation-playbook.md`. 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 ### Input Validation and Sanitization - **Client-side validation**: Form validation security, input pattern enforcement, data type validation - **Allowlist validation**: Whitelist-based input validation, predefined value sets, enumeration security - **Regular expression security**: Safe regex patterns, ReDoS prevention, input format validation - **File upload security**: File type validation, size restrictions, virus scanning integration - **URL validation**: Link validation, protocol restrictions, malicious URL detection - **Real-time validation**: Secure AJAX validation, rate limiting for validation requests ### CSS Handling Security - **Dynamic style sanitization**: CSS property validation, style injection prevention, safe CSS generation - **Inline style alternatives**: External stylesh