---
name: parser
description: "Review file and document processing as a chain of bounded parsing, typed validation, storage, and authorized action."
---

# Parsers, archives, and fail-open

Review file and document processing as a chain of bounded parsing, typed validation, storage, and authorized action.

Defensive study and review of artifacts supplied by their owner. Record missing evidence as an open question.

## Bring to the review

- Parser and upload design
- Accepted file and archive policy
- Owned sample artifacts and unit tests

## Review guide

### 1. Define accepted meaning

Specify supported formats, size and complexity budgets, encoding rules, and the safe typed result each parser may produce.

### 2. Keep parsing contained

Run processing with minimal privileges and isolate it from sensitive filesystem, network, and interpreter authority.

### 3. Validate after parsing

Treat parsed metadata and paths as untrusted until they satisfy an application-specific authorization and storage policy.

### 4. Review failure behavior

Ensure malformed or unsupported input produces a bounded rejection without partial state or public diagnostics.

## What to produce

- Format acceptance contract
- Processing isolation notes
- Failure-handling tests

## Common mistakes

- Trusting declared content type
- Letting parsed paths select storage targets
- Converting parser errors into permissive behavior

## Reading and source context

### Resources

- [Chromium Rule of Two: input trust, memory safety and privilege](https://vulns.co/research/resources/chromium-rule-of-two-input-isolation/)
- [pypdf: bound repeated work when reading embedded attachments](https://vulns.co/research/resources/pypdf-2026-attachment-processing-cost-boundary/)
- [Error Handling Cheat Sheet](https://vulns.co/research/resources/owasp-error-response-data-minimization/)

### Diagrams

- [Parsing safety and action authority](https://vulns.co/research/diagrams/parsing-safety-action-authority/)
- [Failures need separate public and diagnostic contracts](https://vulns.co/research/diagrams/error-diagnostic-disclosure-boundary/)

### Reports

- [V8 optimized object handling retained invalid type assumptions](https://vulns.co/research/reports/google-chrome-v8-type-consistency-2025/)
- [Redis Lua object lifetime failure crossed the scripting boundary](https://vulns.co/research/reports/redis-lua-object-lifetime-isolation-2025/)
- [Facebook error responses exposed unintended application data](https://vulns.co/research/reports/facebook-error-response-data-isolation-2019/)

## Provenance

Editorial guide by vulns.co / GK Data. Updated 2026-10-11.
Library snapshot: 2026-10-04; commit d5550c7891119cf1379e235721541c947850a3b3.
The guide is an editorial synthesis. Linked records preserve their own sources and review dates.

Reader: https://vulns.co/skills/parser/