# Unsafe upload interpretation or placement

Uploaded content is handled in a security-sensitive context beyond its permitted file contract.

**Candidate CWE:** [CWE-434](https://cwe.mitre.org/data/definitions/434.html)

## Test hypothesis

Use a tiny supported baseline. Change filename, declared MIME, and harmless bytes independently in a replica; inspect storage path, processing, retrieval origin, and actual rendering from controlled B.

## Evidence required

Show unsafe interpretation, prohibited placement, or a consequential parser path. Record the exact lifecycle stage and avoid claiming code execution from file acceptance alone.

## Rule out false positives

An unusual extension accepted as inert download, safe isolated hosting, or a file rejected after asynchronous processing is not executable-upload proof.

## Playbook and command references

- [Uploads, downloads, paths, archives, and XML](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/file-boundaries.html) — Follow a file through acceptance, storage, processing, publication, and retrieval while preserving ownership and path boundaries.
- [Browser execution, cross-origin reads, and forged actions](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/browser-trust.html) — Use real browser behavior to distinguish XSS, CSRF, CORS, and messaging failures from header-only leads.

[Find the associated command snippets](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/commands.html?q=Uploads%2C%20downloads%2C%20paths%2C%20archives%2C%20and%20XML)

## Referenced by these target playbooks

[Web & API](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/web-api.html) · [OSS & self-hosted](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/oss.html) · [Mobile](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/mobile.html) · [Desktop & extensions](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/desktop.html) · [AI, agents & MCP](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/ai.html)

## Report checklist

- [ ] Capture the affected version, configuration, identities, and object ownership.
- [ ] Preserve a valid baseline and a negative control.
- [ ] Reproduce the forbidden data access, action, or state change on controlled fixtures.
- [ ] Explain the intended security rule and why the observed behavior violates it.
- [ ] State prerequisites, uncertainty, cleanup, and the smallest demonstrated impact.

## Conditional ATT&CK mapping

No direct ATT&CK mapping selected. Record the weakness and demonstrated impact without forcing an adversary-behavior classification. See the [mapping guide](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/attack.html).

## Primary references

- [PortSwigger file uploads](https://portswigger.net/web-security/file-upload)

[Back to the complete vulnerability catalog](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/vulnerabilities.html)