I initially decided against covering this room, because its relation to cryptocurrency.

Question 1

If not already completed, download the zip folder attached to this task, and open Remix in your preferred browser.

Answer: No answer needed

Question 2

What flag is found after attacking the provided EtherStore Contract?

First we compile both contracts.

Then we deploy EtherStore.Sol on an first account.

Which gives us a deployed contract with 0 balance.

We then set the value to any number (e.g. 10) and hit "deposit" to "give the contract money" (or whatever).

We then copy the address of the EtherStore contract, switch to another account, and add it as a parameter to the Attack.sol contract we then deploy.

Then we set the value to 1, and press "attack" (which steals not 1, but 1 plus the balance in the contract). Oh and the flag!

Of course... One could have simply copied the JS in EtherStore.sol and done the console.log operation ourselves...

Answer: flag{411_ur_37h_15_m1n3}