What is insecure-file-upload?

A guide to testing file-upload features for unsafe validation and storage. It focuses on cases where a website trusts the filename extension or Content-Type instead of checking the file safely.

Use it to review upload endpoints, file-type checks, storage locations, and whether uploaded files can be executed or served to users.

It helps find uploads that could place executable files, browser scripts, malicious documents, or path-traversal archives on the server.

insecure-file-upload — Skill for Claude Code by securityfortech

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.

Any agent

npx skills add securityfortech/hacking-skills --skill insecure-file-upload

Clone the repo

git clone --depth 1 https://github.com/securityfortech/hacking-skills

Made for: Claude Code.

Or install web, the plugin that ships this one along with the rest of its 28 skills.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/securityfortech/hacking-skills/insecure-file-upload/github.svg)](https://agentmods.dev/skills/securityfortech/hacking-skills/insecure-file-upload)

Your own site

<a href="https://agentmods.dev/skills/securityfortech/hacking-skills/insecure-file-upload"><img src="https://agentmods.dev/badge/skills/securityfortech/hacking-skills/insecure-file-upload/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/securityfortech/hacking-skills/insecure-file-upload"><img src="https://agentmods.dev/badge/skills/securityfortech/hacking-skills/insecure-file-upload.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,454 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00000	$0.01454
Opus 5.5	$0.00000	$0.00582
Sonnet 5.5	$0.00000	$0.00291
Haiku 4.5	$0.00000	$0.00145

Measured 2mo ago against content hash 23ef88cb783c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

insecure-file-upload 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 2mo 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.

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.

skills/web/logic/insecure-file-upload/SKILL.md · 146 lines

The source is not reproduced here

No licence file

Read it on GitHub

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.

2mo ago First seen · 146 lines · 0 tokens per session scan A 23ef88cb783c

Subscribe to this mod's changes

insecure-file-upload is a skill published in the GitHub repository securityfortech/hacking-skills (21 stars, last pushed 7mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 1,454 tokens. 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 2026-08-30.

Backend and APIs Security

insecure-file-upload next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
insecure-file-uploadsecurityfortech/hacking-skills	Skill	21	7mo ago	none	A	0	Claude Code
mem0-oss-to-platformmem0ai/mem0	Skill	68k	2d ago	Apache-2.0	A	217	Claude Code, Codex
azure-mgmt-botservice-dotnetmicrosoft/skills	Skill	3.2k	yesterday	MIT	A	78	Claude Code
fastapi-router-pymicrosoft/skills	Skill	3.2k	yesterday	MIT	A	46	Claude Code
dev-runtimelangwatch/langwatch	Skill	5.0k	yesterday	Apache-2.0	A	172	Claude Code
api-designericrisco/rsc-harness	Skill	503	2d ago	MIT	A	105	Claude Code, Codex
migrate-segw-to-raparc-mcp/arc-1	Skill	252	yesterday	MIT	A	106	Claude Code