Unchecked transfer on `FlasherEuler.sol`

[rotcivegaf]

Git branch: M01

Affected smart contract

https://github.com/Fujicracy/fuji-v2/blob/50fd0b74ccee1a73a459118e50e044a2bcfacd10/packages/protocol/src/flashloans/FlasherEuler.sol#L60

Description

The return value of an external transfer call is not checked

Attack scenario

Several tokens do not revert in case of failure and return false If the asset token, extracting from data, used in onFlashLoan function, not reverted or return false if the transfer fails, the token balance will stuck in the contract

Recommendation

Use SafeERC20, or ensure that the transfer return value is checked

[0xdcota]

This issue is addressed in pull request #553.