broken-access-control

broken-access-control is a skill for Claude Code, Codex from scholarly360/owasp-top10-web-skills. It costs 146 tokens per session (2,208 once invoked), scanned B, original, MIT.

A security review guide for finding broken access controls in web applications—cases where users can view or change things they should not.

In plain words
What is it for?
Use it to check routes, ownership checks, cross-origin rules, server-side requests, form protections, and login-session handling in FastAPI or Flask applications.
Why use it?
It helps expose authorization mistakes that can reveal data, allow unwanted changes, or let users gain higher privileges.

Skill for Claude CodeCodex

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

Good fit Use it to check routes, ownership checks, cross-origin rules, server-side requests, form protections, and login-session handling in FastAPI or Flask applications.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/scholarly360/owasp-top10-web-skills/broken-access-control
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 scholarly360/owasp-top10-web-skills --skill broken-access-control
Clone the repo
git clone --depth 1 https://github.com/scholarly360/owasp-top10-web-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 broken-access-control

README.md
[![agentmods](https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/broken-access-control/github.svg)](https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/broken-access-control)
Your own site
<a href="https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/broken-access-control"><img src="https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/broken-access-control/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 broken-access-control

Your own site · 80×15
<a href="https://agentmods.dev/skills/scholarly360/owasp-top10-web-skills/broken-access-control"><img src="https://agentmods.dev/badge/skills/scholarly360/owasp-top10-web-skills/broken-access-control.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 146 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,208 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.00146 $0.02208
Opus 5 $0.00073 $0.01104
Sonnet 5 $0.00029 $0.00442
Haiku 4.5 $0.00015 $0.00221

Measured 12d ago against content hash ae692396c6cd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade B, and why

broken-access-control scanned grade B 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 12d 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.

Cloud metadata endpointmediumServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

**Test vectors:** `http://169.254.169.254/latest/meta-data/` (AWS metadata), `http://localhost:6379` (Redis), `http://10.0.0.1/admin`

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.

from urllib.parse import urlparse
skills/broken-access-control/SKILL.md · 255 lines

How it starts

The opening of the file, as written. The whole thing — 255 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Broken Access Control (A01:2025)

The #1 OWASP risk for two consecutive cycles. Found in 3.74% of applications with over 1.8 million occurrences and 32,654 CVEs. Access control enforces that users cannot act outside their intended permissions. Failures lead to unauthorized data disclosure, modification, or destruction.

For deep reference on all CWEs and remediation patterns, see references/bac-detail.md.


What This Skill Covers

Sub-category Description Key CWEs
Missing Authorization Routes/endpoints with no auth guard CWE-862, CWE-284
IDOR Resource ownership not verified CWE-639, CWE-285
CORS Misconfiguration Wildcard or overly-permissive origins CWE-284
SSRF Outbound requests to internal/private IPs CWE-918
CSRF State-changing forms missing token validation CWE-352
Privilege Escalation Users accessing higher-privilege roles CWE-269
JWT/Session Manipulation Metadata tampering, session fixation CWE-287

Workflow: Auditing a FastAPI or Flask App

Step 1 — Identify All Routes

FastAPI:

# List all routes and their dependencies
for route in app.routes:
    print(route.path, route.methods, route.dependencies)

Flask:

# Print all registered endpoints
for rule in app.url_map.iter_rules():
    print(rule.endpoint, rule.methods, rule.rule)

Flag any route that:

  • Handles POST, PUT, PATCH, DELETE without an auth dependency
  • Returns user-specific data (profile, orders, files) without ownership check
  • Has no rate limiting on sensitive operations

Step 2 — Check Authorization Guards

FastAPI — look for missing Depends():

# VULNERABLE — no auth check
@app.get("/users/{user_id}/data")
async def get_user_data(user_id: int):
    return db.query(UserData).filter_by(owner_id=user_id).all()

# SECURE — requires authenticated user
@app.get("/users/{user_id}/data")
async def get_user_data(user_id: int, current_user: User = Depends(get_current_user)):
    if current_user.id != user_id:
        raise HTTPException(status_code=403, detail="Forbidden")
    return db.query(UserData).filter_by(owner_id=user_id).all()

Read the full file on GitHub · 255 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 12d ago First seen · 255 lines · 146 tokens per session scan B ae692396c6cd

Subscribe to this mod's changes

broken-access-control is a skill published in the GitHub repository scholarly360/owasp-top10-web-skills (22 stars, last pushed 5mo ago), licensed MIT. It adds 146 tokens to every session and 2,208 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it B with 2 findings (cloud metadata endpoint, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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