Welcome to Ethereum Smart Contract Security Masterclass.

Here's how to get maximum value from this course:

Your Learning Path

Weeks 1-2: Foundations — EVM internals, common vulnerability taxonomy (reentrancy, overflow, access control, MEV)

Weeks 3-4: Advanced Vectors — Flash loans, oracle manipulation, proxy pitfalls

Weeks 5-6: Tooling & Methodology — Slither, Mythril, Foundry fuzz testing, Echidna

Weeks 7-8: Case Studies & CTF — Ronin ($625M), Euler ($197M), Curve ($73M), build your own challenges

Weeks 9-10: Career Launch — Portfolio building, bug bounties, client management

Rules

1. Do every lab exercise. Reading about exploits ≠ finding them. Foundry work is non-negotiable.

2. Complete lessons in order. Each builds on the previous.

3. Use the Auditor Lounge chat. Ask questions, share findings, review each other's work.

4. Ship publicly. Post your CTF solutions and audit reports on GitHub/Twitter. Visibility = opportunities.

Setup

curl -L https://foundry.paradigm.xyz | bash && foundryup
pip3 install slither-analyzer

Let's build. 🔒

Over $3 billion was stolen from DeFi protocols in 2022-2023. Here are the five vulnerability classes behind the majority of losses.

---

1. Reentrancy ($150M+)

Started with TheDAO in 2016. Still happening in 2024.

// VULNERABLE
function withdraw() external {
    uint256 amount = balances[msg.sender];
    (bool success, ) = msg.sender.call{value: amount}("");
    balances[msg.sender] = 0; // Too late — attacker already re-entered
}

Modern variants: cross-contract reentrancy, read-only reentrancy (Curve's $73M hack via Vyper compiler bug).

Defense: Checks-Effects-Interactions + reentrancy guards.

---

2. Oracle Manipulation ($500M+)

If your protocol uses AMM spot price as an oracle, it's exploitable. Flash loans give attackers unlimited capital to manipulate reserves atomically.

Defense: TWAPs, Chainlink feeds, multi-oracle strategies with circuit breakers.

---

3. Access Control Failures ($600M+)

The Ronin Bridge ($625M): one org controlled 4/9 validator keys + a temporary permission was never revoked.

Defense: Least privilege. Time-locks. Multi-sig for anything touching funds.

---

4. Flash Loan Amplification ($400M+)

Flash loans aren't a vulnerability — they're an amplifier. Euler Finance ($197M) was one missing health check + a flash loan.

Defense: Assume unlimited attacker capital. Every state-modifying function must enforce invariants.

---

5. Proxy & Upgrade Bugs ($170M+)

Parity wallet ($150M) froze funds permanently via a delegatecall vulnerability.

Defense: Battle-tested proxy libraries. Always initialize implementations. Storage layout checks.

---

I built a comprehensive course covering all of these with real Solidity code, Foundry labs, and professional audit methodology — from Solidity developer to independent smart contract auditor. 🛡️

Over $3 billion was stolen from DeFi protocols in 2022-2023. Here are the five vulnerability classes responsible for the majority — and what every Solidity developer needs to know.

---

1. Reentrancy ($150M+)

Started with TheDAO in 2016. Still happening in 2024.

// VULNERABLE
function withdraw() external {
    uint256 amount = balances[msg.sender];
    (bool success, ) = msg.sender.call{value: amount}("");
    balances[msg.sender] = 0; // Too late — attacker already re-entered
}

Modern variants include cross-contract reentrancy and read-only reentrancy (Curve's $73M hack via a Vyper compiler bug).

Defense: Checks-Effects-Interactions + reentrancy guards.

---

2. Oracle Manipulation ($500M+)

If your protocol uses an AMM's spot price as an oracle, it's exploitable. Flash loans give attackers unlimited capital to manipulate reserves atomically.

Defense: TWAPs, Chainlink feeds, multi-oracle strategies with circuit breakers.

---

3. Access Control Failures ($600M+)

The Ronin Bridge ($625M): one organization controlled 4/9 validator keys + a temporary permission was never revoked.

Defense: Least privilege. Time-locks. Multi-sig for anything touching funds.

---

4. Flash Loan Amplification ($400M+)

Flash loans aren't a vulnerability — they're an amplifier. Euler Finance ($197M) was a single missing health check + a flash loan.

Defense: Assume unlimited attacker capital. Every state-modifying function must enforce invariants.

---

5. Proxy & Upgrade Bugs ($170M+)

Parity wallet ($150M) froze funds permanently via a delegatecall vulnerability.

Defense: Battle-tested proxy libraries. Always initialize implementations. Storage layout checks.

---

I built a comprehensive course covering all of these with real Solidity code, Foundry labs, and professional audit methodology. From Solidity developer to independent auditor — manual review, static analysis, fuzz testing, and real-world case studies. 🛡️

Over $3 billion was stolen from DeFi protocols in 2022-2023 alone. As a smart contract security researcher, I've analyzed hundreds of exploits. Here are the five vulnerability classes responsible for the majority of losses — and what every Solidity developer needs to know.

---

1. Reentrancy — The Original Sin ($150M+)

Started with TheDAO in 2016 ($60M). Still happening in 2024.

The pattern is deceptively simple: a contract sends ETH before updating its state, allowing the recipient to call back in and drain funds.

// VULNERABLE
function withdraw() external {
    uint256 amount = balances[msg.sender];
    (bool success, ) = msg.sender.call{value: amount}("");
    balances[msg.sender] = 0; // Too late — attacker already re-entered
}

Modern variants: Cross-function reentrancy, cross-contract reentrancy, and read-only reentrancy (exploited in Curve's $73M hack via a Vyper compiler bug).

Defense: Checks-Effects-Interactions pattern + reentrancy guards. Always update state before external calls.

---

2. Oracle Manipulation ($500M+)

If your protocol uses an AMM's spot price as an oracle, it's exploitable. Period.

Flash loans give attackers unlimited capital to manipulate reserves. A single transaction can move a Uniswap pool's price 10,000x, borrow against the inflated collateral, and return the flash loan — all atomically.

Defense: Use time-weighted average prices (TWAPs), Chainlink feeds, or multi-oracle strategies with circuit breakers.

---

3. Access Control Failures ($600M+)

The Ronin Bridge hack ($625M) happened because one organization controlled 4 of 9 validator keys, and a temporary DAO permission was never revoked.

Common patterns:

• Missing onlyOwner on critical functions

• Using tx.origin instead of msg.sender

• Unprotected initialize() on proxy implementations

Defense: Principle of least privilege. Time-locks on admin actions. Multi-sig for anything that touches funds.

---

4. Flash Loan Amplification ($400M+)

Flash loans aren't a vulnerability — they're an amplifier. Any small logic error becomes protocol-draining when the attacker can borrow $100M in a single transaction.

The Euler Finance exploit ($197M) combined a flash loan with a single missing health check in a donateToReserves function. One line of code would have prevented it.

Defense: Assume attackers have unlimited capital. Every state-modifying function must enforce protocol invariants.

---

5. Proxy & Upgrade Bugs ($170M+)

The Parity wallet hack ($150M) froze funds permanently due to a delegatecall vulnerability in the library contract.

Modern proxy patterns (UUPS, Transparent, Beacon) introduce storage collision risks, uninitialized implementation contracts, and upgrade authorization bypass.

Defense: Use battle-tested proxy libraries (OpenZeppelin). Always initialize implementations. Test upgrade paths with storage layout checks.

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Want to Go Deeper?

I built a comprehensive course covering all of these vulnerability classes with real Solidity code, Foundry labs, and professional audit methodology.

The course takes you from Solidity developer to independent smart contract auditor — covering manual review techniques, static analysis with Slither & Mythril, fuzz testing with Foundry & Echidna, and real-world case studies of the biggest DeFi hacks.

Check it out if you're serious about Web3 security. 🛡️