Form Validation Breaker

Form Validation Breaker is a skill for Claude Code, Codex from PramodDutta/qaskills. It costs 31 tokens per session (9,677 once invoked), scanned A, original, MIT.

A skill for aggressively testing form validation, the rules that decide whether submitted values are accepted. It checks boundary values, encoded input, injection attempts, and ways to bypass browser-side checks.

In plain words
What is it for?
Use it to test empty and extreme values, malicious input, alternate encodings, and client-versus-server validation.
Why use it?
It helps find validation that works in the browser but can be bypassed by sending requests directly to the server. It also exposes mistakes at the boundaries between forms, servers, databases, and displayed output.

Skill for Claude CodeCodex

Which agent this was written for is unclear — built for aider. Also seen: positional $N argument; mentions Codex; built for aider.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is { name: `${fieldName}_path_traversal`, value: '../../../etc/passwd', category: 'path', expectedResult: 'reject', description: 'Directory traversal' },.

Good fit Use it to test empty and extreme values, malicious input, alternate encodings, and client-versus-server validation.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/PramodDutta/qaskills
agentmods
npx agentmods add skills/pramoddutta/qaskills/form-validation-breaker

Made for: Claude Code, Codex.

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 Form Validation Breaker

README.md
[![agentmods](https://agentmods.dev/badge/skills/pramoddutta/qaskills/form-validation-breaker/github.svg)](https://agentmods.dev/skills/pramoddutta/qaskills/form-validation-breaker)
Your own site
<a href="https://agentmods.dev/skills/pramoddutta/qaskills/form-validation-breaker"><img src="https://agentmods.dev/badge/skills/pramoddutta/qaskills/form-validation-breaker/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 Form Validation Breaker

Your own site · 80×15
<a href="https://agentmods.dev/skills/pramoddutta/qaskills/form-validation-breaker"><img src="https://agentmods.dev/badge/skills/pramoddutta/qaskills/form-validation-breaker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 31 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 9,677 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 5 findings, up to critical

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • critical YARA Match · line 865
    YARA rule matched a known webshell pattern (PHP, Python, JSP, or ASPX webshell).
    Fix: Remove the webshell code immediately. Webshells provide unauthorized remote command execution. Audit the skill for additional backdoors or persistence mechanisms.
  • high Privilege Escalation · line 201
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 203
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 206
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 207
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
How audits are shown
Origin original No closer match found 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 $0.00031 $0.09677
Opus 5 $0.00015 $0.04838
Sonnet 5 $0.00006 $0.01935
Haiku 4.5 $0.00003 $0.00968

Measured 5d ago against content hash f5189d87cd09, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

Form Validation Breaker 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 5d ago.

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.

const response = await this.page.request.fetch(url, {
seed-skills/form-validation-breaker/SKILL.md · 953 lines

How it starts

The opening of the file, as written. The whole thing — 953 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Form Validation Breaker Skill

You are an expert QA security engineer specializing in form validation testing. When the user asks you to test form inputs, break validation logic, or verify server-side protection against malicious input, follow these detailed instructions.

Core Principles

  1. Client-side validation is a convenience, not a defense -- Every form must have server-side validation that mirrors or exceeds client-side rules. Testing must bypass client-side checks to verify the server rejects invalid input.
  2. Boundary values reveal more bugs than random values -- The edges of valid ranges (min, max, min-1, max+1, zero, empty, null) are where validation logic most commonly fails.
  3. Encoding matters as much as content -- The same character can be represented in UTF-8, URL encoding, HTML entities, Unicode escapes, and base64. Validation that blocks <script> but allows %3Cscript%3E is broken.
  4. Test the entire submission pipeline -- A form value passes through DOM event handlers, client-side framework validation, HTTP serialization, server-side parsing, database binding, and output rendering. Each stage can transform or mishandle the input.
  5. Every input type has unique attack vectors -- Text fields, email inputs, file uploads, dropdowns, checkboxes, hidden fields, date pickers, and rich text editors each have distinct failure modes. Test each type specifically.
  6. Multi-step forms have inter-step vulnerabilities -- When a form spans multiple pages or tabs, state can leak between steps. Manipulating step order, replaying previous steps, or submitting incomplete flows exposes logic bugs.
  7. Validation error messages should not leak implementation details -- Error messages like "SQL syntax error" or "column 'users.email' not found" reveal the database schema. Verify that error messages are generic and user-friendly.

Project Structure

Organize your form validation testing suite with this structure:

tests/
  form-validation/
    boundary-values.spec.ts
    injection-payloads.spec.ts
    encoding-edge-cases.spec.ts
    file-upload-validation.spec.ts
    client-bypass.spec.ts
    multi-step-forms.spec.ts
    real-time-validation.spec.ts
  fixtures/
    form-breaker.fixture.ts
  helpers/
    payload-generator.ts
    boundary-calculator.ts
    encoding-transformer.ts
    validation-reporter.ts
  payloads/
    xss-vectors.json
    sql-injection.json
    unicode-edge-cases.json
playwright.config.ts

Read the full file on GitHub · 953 lines

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. 5d ago First seen · 953 lines · 31 tokens per session scan A f5189d87cd09

Subscribe to this mod's changes

Form Validation Breaker is a skill published in the GitHub repository PramodDutta/qaskills (219 stars, last pushed 9d ago), licensed MIT. It adds 31 tokens to every session and 9,677 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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