First Flight #22: Steaking

Summary

The stake() function does not increase user staked amount if user has staked before.
This will cause lost of fund for user and lost off shares they received.

Vulnerability Details

When user deposits fund into the contract, the stake() function will set the user's deposited amount to the last amount they deposited.

• user stakes 1 ETH -> balance: 1 ETH

• user stakes an other 0.5 ETH -> balance: 0.5 ETH, but expecting balance is: 1.5 ETH

• user now decides to unstakes all their stakes (1.5 ETH), but because the recorded user's balance is 0.5 ETH, they can only withdraw/get back upto 0.5 ETH, making their 1 ETH stuck forever

• if they deposits into vault, they will only get shares by their recorded balance, mean 0.5 ETH, but expecting they get shares equivalent to their deposited amount (1.5 ETH)

Impact

Since the user's staked amount get overwritten, user can't withdraw their full deposited amount.
The fund then will be stuck on the contract forever.

Also because their staked balance will affect their received shares, so they will not get the full amount of shares as their expectation.

Tools Used

Manual review

Recommendations

Increase usersToStakes up on user stakes: