QA Report

[code423n4]

1. Wrong logic

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L461

Summary

As in the comment, "add and fail loud if zero address or already present and not deprecated".
It should be
'''

if (gauge == address(0) || !(newAdd && previouslyDeprecated)) 

'''
Insted of
'''

if (gauge == address(0) || !(newAdd || previouslyDeprecated)) 

'''

[Joeysantoro]

The failure case for this clause should be where both newAdd and previouslyDeprecated are true. "A not new address must be not deprecated". all other cases should not fail.

Your proposed solution would fail in two undesirable cases, when one is true but not the other.

[0xean]

closing as invalid.