Curriculum·J301 Chains, Layer 2s, and Bridges·about 31 min
The scaling landscape
By the end of this lesson you can
- →Explain what a rollup inherits from its base chain and what it does not
- →Determine whether an address you control on one chain is yours on another
- →Decompose an L2 transaction fee into the components that actually drive it
- →Identify the upgrade authority behind any chain you hold value on
Junior · enrolled learners
This lesson opens with Wintermute and Optimism, June 2022.
- What happened
- The Optimism Foundation agreed to send 20 million OP tokens to the market maker Wintermute, which supplied a multisig address. Optimism sent two test transactions, Wintermute confirmed them, and the 20 million tokens followed. Wintermute then found it could not control them. The address was a Gnosis Safe deployed on Ethereum mainnet and not deployed on Optimism, so on Optimism it was an address with no code behind it. An attacker deployed a Safe at that same address on Optimism first, taking control of the tokens, worth roughly $17.6M at the time. The disclosure came on 9 June 2022 from both parties.
- The decision point
- Wintermute assumed that controlling a multisig at an address on Ethereum meant controlling anything sent to that address on another EVM chain, which is true for an ordinary key-controlled account and false for a contract. A contract address is a slot, and the party who deploys into that slot on a given chain owns it there. The two test transactions confirmed that the tokens arrived, which was never the question, and confirmed nothing about who could move them afterwards.
- Recorded loss
- $17,600,000
What you will be able to answer
- →Is your address on one EVM chain yours on another?
- →What does a rollup inherit from its base chain?
- →What actually drives an L2 fee?
- →What did the two test transactions prove?
Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.
It is free. We do not sell the list and there is nothing to buy at the end of it.
Sources and review
- https://slowmist.medium.com/slowmist-key-to-the-theft-of-20-million-op-tokens-transaction-replay-490baaf45f26
- https://inspexco.medium.com/how-20-million-op-was-stolen-from-the-multisig-wallet-not-yet-owned-by-wintermute-3f6c75db740a
- https://thedefiant.io/optimism-20m-exploit
- https://l2beat.com/scaling/summary
Confidence high·Volatility high·Reviewed 2026-08-06·Owner unassigned
Contested
F101 establishes that a self-custody send to the wrong EVM network is usually recoverable, because the same private key controls the identical address on both chains. That remains correct and this lesson is its boundary case: the reasoning holds for key-controlled accounts and fails for contract accounts. Teach both together or the first becomes dangerous.
Rollup classifications change as teams ship. Any statement about which chains have removed which training wheels is dated on the day it is written, which is why this lesson teaches the questions and points at a tracker rather than listing current answers.