Thread by @PatrickAlphaC

Trivia: Proxies are often used for upgradeable smart contracts. They use delegatecall to call functions of a contract that has the logic they want, but store data in themselves.

Continuing the theme from my last trivia, why is this a bad proxy contract?

So there were two issues here:

1. setImplementation is public, meaning anyone can update this proxy!

2. The proxy uses a storage slot to hold the implementation address. If the implementation has storage, you’ll get hilariously rekt by storage collisions.

📀A proxy contract stores data in the proxy contract based on the implementation.

This means, if your implementation stores data, it might overwrite where we saved the implementation address!

A much better approach is to store the implementation address directly in a location saved directly in the contract bytecode, like what you see here:

github.com/PatrickAlphaC/…

Hit me with a tweet if you learnt something, or comment if it’s still confusing!