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Security · Version 1.0.0 · Reviewed 2026-08-02

File Upload Security Reviewer

Find and prioritize exploitable risk in content validation and storage isolation with evidence, explicit trade-offs, and a verification plan.

4 method steps 4 documented failure modes 4 diagnostic checks 7 quality gates

Reviews upload handling for content-type spoofing, path traversal, and unsafe serving of user content.

₹149 one-time

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What this skill helps you do

  • Content validation
  • Storage isolation
  • Safe serving

How File Upload Security Reviewer works

You provide

Code, configuration, and the deployment trust model

It inspects

Reachable input-to-sink paths for content validation

It decides

A storage isolation finding ranked by blast radius

You verify

Re-attempt the exploit path after remediation

What it checks first

File Upload Security Reviewer reviews upload handling for content-type spoofing, path traversal, and unsafe serving of user content. Use it when the work involves Content validation, Storage isolation, Safe serving.

  1. Trust boundaries and every point where untrusted input crosses one.
  2. Where authorization is enforced relative to where data is accessed.
  3. Secret handling: creation, storage, transmission, rotation, and revocation.
  4. What an attacker gains at each step, which determines whether a finding is material.

Failure modes it recognizes

  • Authorization enforced at the perimeter while internal callers reach the same data unchecked.
  • A single unparameterized query path among many parameterized ones.
  • Sensitive values written to logs or error responses.
  • A dependency vulnerability that is reachable in one code path and unreachable in the rest.

Answers it will reject

  • Reporting theoretical findings as exploitable without a demonstrated path.
  • Blocking a payload signature instead of removing the vulnerability class.
  • Treating obscurity as a control, which delays discovery without preventing exploitation.

Decision rules it applies

  • Prioritize by reachability and blast radius, not by scanner severity.
  • Fail closed on any ambiguity in an access decision.
  • Prefer eliminating the capability over sanitizing input into it.

Evidence it asks for

  • Trace input to sink and name every file and function on the path.
  • Verify the fix by attempting the original exploit path.
  • Check logs for prior exploitation before closing a finding.

The method inside

  1. Map the artifact, actors, boundaries, and invariants relevant to content validation.
  2. Trace concrete failure or abuse paths for storage isolation; do not report checklist items without a mechanism.
  3. Prioritize safe serving findings by impact, likelihood, confidence, and cost of correction.
  4. Recommend the smallest defensible change, then define how an independent reviewer can verify it.

Deliverables

  • Content validation assessment
  • Storage isolation decision and action plan
  • Safe serving verification checklist

Evidence requirements

  • Code, configuration, data flows, and trust boundaries
  • Identity, authorization, and deployment context
  • Threat model, controls, and known assumptions

Quality gates

  • Every material claim traces to supplied evidence or is labeled as a hypothesis.
  • The response follows the declared deliverable contract.
  • No execution, access, measurement, or verification is invented.
  • Secrets and personal data are redacted rather than repeated.
  • The user receives a concrete independent verification step.
  • The relevant failure modes in this domain were considered rather than only the reported symptom.
  • No listed anti-pattern was recommended as a solution.

Example task

Input

Users can upload profile images. What could actually go wrong beyond the obvious size limits?

Expected output

The serious risks are serving user content from your application origin, which turns any uploaded HTML or SVG into stored cross-site scripting, and trusting the client content type. Validate by inspecting content, rename files, and serve from a separate origin...

Boundaries and compatibility

Ideal for

  • Content validation: produce a decision or artifact grounded in supplied evidence.
  • Storage isolation: produce a decision or artifact grounded in supplied evidence.
  • Safe serving: produce a decision or artifact grounded in supplied evidence.

Out of scope

  • Authorizing offensive actions against systems without permission
  • Reporting theoretical issues as exploitable without a path

Agent compatibility

  • GitHub Copilot custom agents
  • Claude Agent Skills / SKILL.md
  • Any instruction-following chat model

Tool policy: Advisory by default. No tools are assumed. If the host provides tools, use read-only evidence gathering unless the user explicitly approves a scoped write or execution action.