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ClaudSkills / Security / web-security

Harden API Security

Category: Security  ·  Sub-category: web-security  ·  Last updated:
Defensive methodology for API-layer abuse across REST, gRPC, and WebSocket: broken object- and function-level authorization (BOLA/BFLA), broken authentication and token replay, mass assignment, SSRF from URL-accepting parameters, and unrestricted resource consumption (MITRE ATT&CK T1190, T1078, T1528, T1552.005, T1499.003). Keys off API gateway and reverse-proxy access logs (AWS API Gateway, Azure APIM, Kong, Envoy/Istio), WAF logs (AWS WAF, Azure Front Door/App Gateway), and application authorization-decision logs. Gives the defender view, log sources, a detection approach pointing to public rule sources, a hypothesis-driven hunt, and gateway plus authorization hardening. Use when hardening a REST/gRPC/WebSocket API, writing API-abuse detections, hunting for BOLA/IDOR enumeration or BFLA, triaging bursts of 401/403/429 on an API gateway, or designing edge authorization and schema-validation controls.
Security AStatic scan found no risk patternsHow grading works ›

What this skill does

Harden API Security is a community-contributed Claude Code skill in the web-security sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/harden-api-security/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when hardening a REST/gRPC/WebSocket API, writing API-abuse detections, hunting for BOLA/IDOR enumeration or BFLA, triaging bursts of 401/403/429 on an API gateway, or designing edge authorization and schema-validation controls.

Who uses this skill

The Harden API Security Claude Code skill is built for security engineers, penetration testers, DevSecOps practitioners, and development teams hardening codebases and infrastructure. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 211,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/harden-api-security
curl -L https://claudskills.com/skills/harden-api-security/SKILL.md \
  -o ~/.claude/skills/harden-api-security/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/harden-api-security/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/harden-api-security/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\harden-api-security\SKILL.md on Windows. See the full install guide for step-by-step instructions.

Telegram

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Harden API Security Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/harden-api-security/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.
What does the Harden API Security skill do?
Defensive methodology for API-layer abuse across REST, gRPC, and WebSocket: broken object- and function-level authorization (BOLA/BFLA), broken authentication and token replay, mass assignment, SSRF from URL-accepting parameters, and unrestricted resource consumption (MITRE ATT&CK T1190, T1078, T1528, T1552.005, T1499.003). Keys off API gateway and reverse-proxy access logs (AWS API Gateway, Azure APIM, Kong, Envoy/Istio), WAF logs (AWS WAF, Azure Front Door/App Gateway), and application authorization-decision logs. Gives the defender view, log sources, a detection approach pointing to public rule sources, a hypothesis-driven hunt, and gateway plus authorization hardening. Use when hardening a REST/gRPC/WebSocket API, writing API-abuse detections, hunting for BOLA/IDOR enumeration or BFLA, triaging bursts of 401/403/429 on an API gateway, or designing edge authorization and schema-validation controls.
Is this skill free to install?
Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.
When should I use the Harden API Security skill?
Use Harden API Security when your Claude Code task falls under the Security category — specifically in the web security area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Harden API Security" or describe the task and let Claude pick). Browse related skills at /category/security/.
What is a Claude Code skill and how does the Harden API Security skill fit in?
A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Harden API Security is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Security category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA
umbrasec-labs. (2026). Harden API Security [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/harden-api-security/
BibTeX
@misc{harden-api-security-2026,
  author    = {umbrasec-labs},
  title     = {Harden API Security [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/harden-api-security/}
}

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Security scan

Grade A · scanned 2026-10-25 — free static scan against the OWASP Agentic Skills Top 10.

The scan flagged 2 of 10 categories (data-exfil, network), including a high-severity pattern. Patterns shown inside code fences are weighted as examples rather than instructions — read the grading methodology for what this does and does not guarantee.

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[![Security: A](https://img.shields.io/badge/Security-A-2e7d32)](https://claudskills.com/skills/harden-api-security/#security)

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More Security skills

Browse all Security skills in the ClaudSkills registry, or explore these other picks from the same category:

Browse all Security skills → Top 100 skills
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