Submitted by p4st13r4, also found by hansfriese, Ruhum, TerrierLover, WatchPug, and zzzitron
Affected code:
WETH.sol is almost copied from the infamous WETH contract that lives in mainnet. This contract is supposed to receive the native currency of the blockchain (for example ETH) and wrap it into a tokenized, ERC-20 form. This contract computes the totalSupply() using the balance of the contract itself stored in the balanceOf mapping, when instead it should be using the native balance function. This way, totalSupply() always returns zero as the WETH contract itself has no way of calling deposit to itself and increase its own balance
Editor
tkkwon1998 (Canto) confirmed
Alex the Entreprenerd (judge) commented:
