A security-testing guide for finding Broken Object Level Authorization (BOLA), also called Insecure Direct Object Reference (IDOR), where a user can access another user's resource by changing its identifier.

It is for testing API and web application URLs, request bodies, downloads, and other operations that accept user, order, invoice, or other resource IDs.

It exposes missing ownership checks that may let users read, change, or delete records belonging to someone else.

bola-idor — Skill for Claude Code and Codex by SecurityTalent

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 SecurityTalent/bugskill-ai --skill bola-idor

Clone the repo

git clone --depth 1 https://github.com/SecurityTalent/bugskill-ai

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/bola-idor/github.svg)](https://agentmods.dev/skills/securitytalent/bugskill-ai/bola-idor)

Your own site

<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/bola-idor"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/bola-idor/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/bola-idor"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/bola-idor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 107 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,863 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.

Origin 100% copy Near-identical to another mod 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.

Model	Per session	Once invoked
Fable 5.1	$0.00107	$0.01863
Opus 5.5	$0.00043	$0.00745
Sonnet 5.5	$0.00021	$0.00373
Haiku 4.5	$0.00011	$0.00186

Measured 20d ago against content hash 01c60b97fb2b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

bola-idor 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 20d 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.

compatibility: Designed for Claude Code. Burp Suite (Autorize extension) or curl recommended.

Origin

This is a copy

100% identical to bola-idor — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

Awesome-Claude-Code-Agent-Skills/03-Authentication-and-Access-Control/bola-idor/SKILL.md · 155 lines

How it starts

The opening of the file, as written. The whole thing — 155 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Broken Object Level Authorization (BOLA / IDOR)

What Is Broken and Why

The server accepts a resource identifier from the client and fetches the object without verifying the requesting user owns or has access to it. Authorization is enforced at the route level ("is this user logged in?") but not at the object level ("does this user own object 1042?"). An attacker substitutes their identifier for a victim's to read, modify, or delete resources they should never access. BOLA is consistently the #1 OWASP API Security risk because it is trivial to test and almost always yields high-severity findings.

Key Signals

Numeric or sequential IDs in URL path: /api/orders/1042, /users/7/profile
UUIDs or hashes in query params or body referencing another user's object
Parameters named user_id, account_id, owner_id, ref, target_id, invoice
Write operations (PUT/PATCH/DELETE) accepting an object ID
Export/download/share endpoints with a resource ID parameter
Keywords me or current used as ID aliases — swappable for integer IDs
Older API versions still accessible: /v1/, /v2/, /legacy/
UUIDs discoverable via public profiles, share links, password reset flows, Wayback Machine

Methodology

Map all object identifiers across the entire app — URLs, query params, request body, cookies, headers.
Create two accounts with distinctive names (e.g. attacker_a, victim_b). Use separate browsers to keep sessions fully isolated. Fully populate the victim account with varied resources and document all encountered IDs. Capture all requests with the victim session.
Replay each request using the attacker token with the victim's object IDs.
Compare responses — same data returned = BOLA confirmed.
Test unauthenticated: remove Authorization header entirely.
Test write operations (PUT/PATCH/DELETE) — impact is higher than reads.
Test indirect references: export endpoints, share links, scheduled jobs, email triggers.
Test less-visible features: auto-save, draft, notification, audit log, attachment endpoints.
Try older API versions (/v1/, /beta/) which often lack access control patches.
For second-order IDOR: store a payload referencing victim's ID, trigger async processing, observe outcome.

Read the full file on GitHub · 155 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.

20d ago First seen · 155 lines · 107 tokens per session scan A 01c60b97fb2b

Subscribe to this mod's changes

bola-idor is a skill published in the GitHub repository SecurityTalent/bugskill-ai (13 stars, last pushed 21d ago), licensed MIT. It adds 107 tokens to every session and 1,863 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to bola-idor, differing in 0 lines, and is treated as a copy.

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