defi-attack-patterns

defi-attack-patterns is a skill for Claude Code, Codex from JustineDevs/premortem. It costs 46 tokens per session (3,343 once invoked), scanned A, a copy of defi-attack-patterns, Apache-2.0.

A security playbook for finding and understanding attacks against decentralized finance systems, which are financial applications running on blockchains. It covers flash loans, price-oracle manipulation, transaction-order attacks, governance, bridges, and token behavior.

In plain words
What is it for?
Use it when assessing DeFi protocols, smart-contract integrations, price feeds, lending and liquidation logic, governance systems, bridges, or token-standard edge cases.
Why use it?
It helps reviewers recognize how DeFi systems can be manipulated, including the fact that a flash-loan attack must borrow, use, and repay funds within one transaction.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/justinedevs/premortem/defi-attack-patterns
Any agent
npx skills add JustineDevs/premortem --skill defi-attack-patterns
Clone the repo
git clone --depth 1 https://github.com/JustineDevs/premortem

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 defi-attack-patterns

README.md
[![agentmods](https://agentmods.dev/badge/skills/justinedevs/premortem/defi-attack-patterns.svg)](https://agentmods.dev/skills/justinedevs/premortem/defi-attack-patterns)
Your own site
<a href="https://agentmods.dev/skills/justinedevs/premortem/defi-attack-patterns"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/defi-attack-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,343 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00046 $0.03343
Opus 5 $0.00023 $0.01672
Sonnet 5 $0.00009 $0.00669
Haiku 4.5 $0.00005 $0.00334

Measured 5d ago against content hash 8b80984dea98, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

defi-attack-patterns 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 5d 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.

Origin

This is a copy

100% identical to defi-attack-patterns — 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.

.agents/skills/defi-attack-patterns/SKILL.md · 356 lines

How it starts

The opening of the file, as written. The whole thing — 356 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SKILL: DeFi Attack Patterns — Expert Attack Playbook

AI LOAD INSTRUCTION: Expert DeFi exploitation techniques. Covers flash loan mechanics, oracle manipulation (spot vs TWAP), MEV extraction (sandwich, JIT, liquidation), precision loss attacks, governance exploits, bridge vulnerabilities, and token standard pitfalls. Base models often miss the single-transaction atomicity constraint of flash loans and the distinction between spot price and TWAP manipulation.


1. FLASH LOAN ATTACKS

1.1 Mechanism

Flash loans provide uncollateralized borrowing within a single transaction. The entire borrow → use → repay cycle must complete atomically; if repayment fails, the transaction reverts as if nothing happened.

Provider Max Amount Fee
Aave V3 Pool liquidity per asset 0.05% (can be 0 for approved borrowers)
dYdX Pool liquidity 0 (uses internal balance manipulation)
Uniswap V3 Pool liquidity per pair 0.3% (swap fee tier)
Balancer Pool liquidity Protocol-configurable

1.2 Price Oracle Manipulation

1. Flash borrow 100,000 WETH
2. Swap 100,000 WETH → TOKEN on AMM_A
   → TOKEN spot price on AMM_A skyrockets
3. On Lending_Protocol (reads AMM_A spot price as oracle):
   → Deposit small TOKEN collateral (valued at inflated price)
   → Borrow large amount of WETH against it
4. Swap TOKEN back → WETH on AMM_A (restore price)
5. Repay flash loan (100,000 WETH + fee)
6. Keep borrowed WETH from Lending_Protocol minus collateral cost

Key insight: protocols using AMM spot reserves (getReserves()) as price oracles are vulnerable. Must use TWAP or external oracle (Chainlink).

Read the full file on GitHub · 356 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. 5d ago First seen · 356 lines · 46 tokens per session scan A 8b80984dea98

Subscribe to this mod's changes

defi-attack-patterns is a skill published in the GitHub repository JustineDevs/premortem (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 46 tokens to every session and 3,343 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to defi-attack-patterns, differing in 0 lines, and is treated as a copy.

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