How do I install the Web File Upload skill?

Run npx skillmds@latest add noorqureshi/web-file-upload in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Web File Upload safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Web File Upload?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Web File Upload free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Web File Upload?

NoorQureshi (@noorqureshi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Web File Upload by noorqureshi — Agent Skill

Name: Web File Upload
Author: NoorQureshi

Web File Upload

Turn a file upload into RCE or stored XSS/SSRF. Load on any upload: avatars, attachments, import CSV/XML, profile images, document processors, "upload your resume". Signals: multipart/form-data, filename in response, an uploads/ path, image thumbnailing, PDF/office parsing.

NoorQureshi e3b5adc 2 files · 5.0 KB Updated Sep 17, 2026

File contents

Malicious file upload

When it applies

The app accepts a file and later stores, serves, parses, or converts it. Impact depends on what happens to the file after upload — served from webroot? passed to a parser? rendered?

Why it works

Validation is usually on the wrong signal (extension or Content-Type, both attacker-set) while the dangerous behaviour is downstream: the web server executes .php in the uploads dir, a parser follows external entities, or the file is served with an HTML content-type.

Method

Payloads & full variation set: cheatsheet.md next to this file — work the set, not the first line.

Find the after-upload behaviour: where is it stored, what URL serves it, what parses it?
RCE via executable extension when uploads are under a script-executing webroot: upload shell.php; if blocked, try .phtml .php5 .phar, double ext shell.php.jpg, null byte shell.php%00.jpg, case .pHp, trailing dot/space, or a polyglot (valid JPEG + PHP in a comment) with a .php name.
Content-Type / magic-byte bypass: keep a real image header (GIF89a;) then payload; change the multipart Content-Type to image/png while the name stays .php.
Parser-based: SVG upload → XSS/SSRF/XXE (SVG is XML+script); office/PDF → SSRF/XXE via external resources; image libraries (ImageMagick) → command exec via crafted files.
Path traversal in filename: ../../var/www/html/shell.php to escape the uploads dir.

Gotchas

Upload succeeds but stored outside webroot / served as text/plain → no RCE; pivot to XSS/SSRF instead.
Random server-side filenames defeat direct access — look for a predictable/leaked path.
WAF strips <?php → use <?= or <script language="php">.

Verify success

Browse to the uploaded script and get command output, or the SVG/XML fires in a victim context / triggers an OOB callback.

References

PortSwigger file-upload labs; OWASP Unrestricted File Upload.

---name: web-file-uploaddescription: Turn a file upload into RCE or stored XSS/SSRF. Load on any upload: avatars, attachments, import CSV/XML, profile images, document processors, "upload your resume". Signals: multipart/form-data, filename in response, an uploads/ path, image thumbnailing, PDF/office parsing.---# Malicious file upload## When it appliesThe app accepts a file and later stores, serves, parses, or converts it. Impact depends onwhat happens to the file after upload — served from webroot? passed to a parser? rendered?## Why it worksValidation is usually on the wrong signal (extension or `Content-Type`, both attacker-set)while the dangerous behaviour is downstream: the web server executes `.php` in the uploadsdir, a parser follows external entities, or the file is served with an HTML content-type.## Method> **Payloads & full variation set:** [`cheatsheet.md`](cheatsheet.md) next to this file — work the set, not the first line.1. **Find the after-upload behaviour**: where is it stored, what URL serves it, what parses it?2. **RCE via executable extension** when uploads are under a script-executing webroot: upload `shell.php`; if blocked, try `.phtml .php5 .phar`, double ext `shell.php.jpg`, null byte `shell.php%00.jpg`, case `.pHp`, trailing dot/space, or a polyglot (valid JPEG + PHP in a comment) with a `.php` name.3. **Content-Type / magic-byte bypass**: keep a real image header (`GIF89a;`) then payload; change the multipart `Content-Type` to `image/png` while the name stays `.php`.4. **Parser-based**: SVG upload → XSS/SSRF/XXE (SVG is XML+script); office/PDF → SSRF/XXE via external resources; image libraries (ImageMagick) → command exec via crafted files.5. **Path traversal in filename**: `../../var/www/html/shell.php` to escape the uploads dir.## Gotchas- Upload succeeds but stored outside webroot / served as `text/plain` → no RCE; pivot to XSS/SSRF instead.- Random server-side filenames defeat direct access — look for a predictable/leaked path.- WAF strips `<?php` → use `<?=` or `<script language="php">`.## Verify successBrowse to the uploaded script and get command output, or the SVG/XML fires in a victimcontext / triggers an OOB callback.## ReferencesPortSwigger file-upload labs; OWASP Unrestricted File Upload.

Frequently asked questions