HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
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.
npx skills add yaklang/hack-skills --skill race-conditiongit clone --depth 1 https://github.com/yaklang/hack-skillsWrote 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.
[](https://agentmods.dev/skills/yaklang/hack-skills/race-condition)<a href="https://agentmods.dev/skills/yaklang/hack-skills/race-condition"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/race-condition.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00050 | $0.05005 |
| Opus 5 | $0.00025 | $0.02502 |
| Sonnet 5 | $0.00010 | $0.01001 |
| Haiku 4.5 | $0.00005 | $0.00500 |
Grade A, and why
race-condition scanned grade A with 0 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 3d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
3 near-identical copies found in the catalogue:
- race-condition — 100% identical, 0 lines differ
- race-condition — 100% identical, 0 lines differ
- race-condition — 100% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 527 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Race Conditions — Testing & Exploitation Playbook
AI LOAD INSTRUCTION: Treat race conditions as authorization/state integrity issues: non-atomic read-then-write lets multiple requests observe stale state. Prioritize one-time or balance-like operations. Combine parallel transport (HTTP/1.1 last-byte sync, HTTP/2 single-packet, Turbo Intruder gates) with application evidence (duplicate success responses, inconsistent balances, duplicate ledger rows). Authorized testing only. Routing note: for business workflows, coupons, inventory, or one-time rewards, start with this skill and cross-load
business-logic-vulnerabilities.
0. QUICK START — What to Test First
Target endpoints where check and update are unlikely to be a single atomic database operation:
| Priority | Operation class | Example paths / parameters |
|---|---|---|
| 1 | One-time redeem / coupon / bonus | redeem, apply_coupon, claim_reward, voucher |
| 2 | Balance / quota / stock deduction | transfer, purchase, reserve, inventory |
| 3 | Invite / referral / signup bonus | invite_accept, referral_claim |
| 4 | Password / email / MFA verification | verify_token, confirm_email, reset_password |
| 5 | Idempotent-looking APIs without strong keys | POST that should succeed only once per user |
First moves (conceptual):
- Capture the state-changing request in a proxy.
- Send 20–100 copies as simultaneously as your tooling allows.
- Classify outcome: 0/1 expected successes vs N successes or inconsistent final state.
1. CORE CONCEPT
1.1 TOCTOU (Time-of-check to time-of-use)
Thread A Thread B
| |
+-- CHECK (resource OK) |
| +-- CHECK (resource OK) ← both see "OK"
+-- USE / UPDATE |
| +-- USE / UPDATE ← duplicate effect
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.
- 3d ago First seen · 527 lines · 50 tokens per session scan A 2fc1e1623968
race-condition is a skill published in the GitHub repository yaklang/hack-skills (2,098 stars, last pushed 2mo ago), licensed MIT. It adds 50 tokens to every session and 5,005 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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