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
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/yaklang/hack-skillsnpx agentmods add skills/yaklang/hack-skills/smart-contract-vulnerabilitiesWrote 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/smart-contract-vulnerabilities)<a href="https://agentmods.dev/skills/yaklang/hack-skills/smart-contract-vulnerabilities"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/smart-contract-vulnerabilities/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.
<a href="https://agentmods.dev/skills/yaklang/hack-skills/smart-contract-vulnerabilities"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/smart-contract-vulnerabilities.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket warn
- Snyk fail
- NVIDIA SkillSpector warn
SkillSpector: 1 finding, 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 MCP Rug Pull · line 262 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
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 | $0.00046 | $0.03000 |
| Opus 5 | $0.00023 | $0.01500 |
| Sonnet 5 | $0.00009 | $0.00600 |
| Haiku 4.5 | $0.00005 | $0.00300 |
Grade A, and why
smart-contract-vulnerabilities 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 6d 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:
- smart-contract-vulnerabilities — 100% identical, 0 lines differ
- smart-contract-vulnerabilities — 100% identical, 0 lines differ
- smart-contract-vulnerabilities — 97% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 315 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Smart Contract Vulnerabilities — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert smart contract audit techniques. Covers reentrancy (single, cross-function, cross-contract, read-only), integer overflow, access control, delegatecall, randomness manipulation, flash loans, signature replay, front-running/MEV, and CREATE2 exploitation. Base models miss subtle cross-contract reentrancy and storage layout collisions in proxy patterns.
0. RELATED ROUTING
- defi-attack-patterns when the vulnerability is part of a DeFi protocol exploit (flash loans, oracle manipulation, governance attacks)
- deserialization-insecure when the target is off-chain infrastructure deserializing blockchain data
Advanced Reference
Also load SOLIDITY_VULN_PATTERNS.md when you need:
- Side-by-side vulnerable vs fixed code patterns for each vulnerability class
- Gas optimization traps that introduce vulnerabilities
- Proxy pattern storage collision examples with slot calculations
1. REENTRANCY
The most iconic smart contract vulnerability. External calls transfer execution control; if state is not updated before the call, the callee can re-enter.
1.1 Classic Reentrancy (Single-Function)
Victim.withdraw()
├── checks balance[msg.sender] > 0 ✓
├── msg.sender.call{value: balance}("") ← external call
│ └── Attacker.receive()
│ └── Victim.withdraw() ← re-enters before state update
│ ├── checks balance[msg.sender] ← still > 0!
│ └── sends ETH again
└── balance[msg.sender] = 0 ← too late
1.2 Cross-Function Reentrancy
Two functions share state; attacker re-enters a different function during callback:
| Step | Execution | State |
|---|---|---|
| 1 | Call withdraw() → external call |
balance still positive |
| 2 | Attacker fallback calls transfer(attacker2) |
balance used before reset |
| 3 | transfer reads stale balance → moves funds |
attacker2 receives tokens |
| 4 | Original withdraw completes, zeroes balance |
damage done |
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.
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.
- 6d ago First seen · 315 lines · 46 tokens per session scan A 58641f7bcd78
smart-contract-vulnerabilities is a skill published in the GitHub repository yaklang/hack-skills (2,143 stars, last pushed 2mo ago), licensed MIT. It adds 46 tokens to every session and 3,000 once invoked, about $0.0002 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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