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file-upload-security

Category: Security  ·  Sub-category: web-security  ·  Last updated:
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Accept user file uploads without introducing remote code execution, stored XSS, or polyglot attacks. Covers magic-byte validation, strict type allowlists, image re-encoding to defang embedded payloads, EXIF stripping, virus scanning, path-safe storage keys, and serving via a separate origin with Content-Disposition. Invoke when adding upload to a new endpoint or migrating from local-disk storage to object storage.
Security AStatic scan found no risk patternsHow grading works ›

From the source SKILL.md

User-uploaded files are one of the highest-leverage attack surfaces. A single endpoint that accepts * MIME types and writes to a server-served path is a path to RCE, XSS, SSRF, stored-XSS in PDFs, and a half-dozen other failure modes. The defaults of every web framework do less than they should — this skill is what to add on top.

What this skill does

file-upload-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/gw360--file-upload-security/ and loads when your prompt matches the skill's trigger.

Who uses this skill

The file-upload-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 146,000+ 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/gw360--file-upload-security
curl -L https://claudskills.com/skills/gw360--file-upload-security/SKILL.md \
  -o ~/.claude/skills/gw360--file-upload-security/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/gw360--file-upload-security/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/gw360--file-upload-security/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\gw360--file-upload-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 file-upload-security Claude Code skill?
Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/gw360--file-upload-security/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.
What does the file-upload-security skill do?
Accept user file uploads without introducing remote code execution, stored XSS, or polyglot attacks. Covers magic-byte validation, strict type allowlists, image re-encoding to defang embedded payloads, EXIF stripping, virus scanning, path-safe storage keys, and serving via a separate origin with Content-Disposition. Invoke when adding upload to a new endpoint or migrating from local-disk storage to object storage.
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 file-upload-security skill?
Use file-upload-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 file-upload-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 file-upload-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. file-upload-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
phamlongh230-lgtm. (2026). file-upload-security [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/gw360--file-upload-security/
BibTeX
@misc{gw360--file-upload-security-2026,
  author    = {phamlongh230-lgtm},
  title     = {file-upload-security [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/gw360--file-upload-security/}
}

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Security scan

Grade A · scanned 2026-07-06 — free static scan against the OWASP Agentic Skills Top 10.

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

Show this grade on your repo (click to copy):

[![Security: A](https://img.shields.io/badge/Security-A-2e7d32)](https://claudskills.com/skills/gw360--file-upload-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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