Submitted by hansfriese, also found by csanuragjain and unforgiven
https://github.com/code-423n4/2022-05-backd/tree/main/protocol/contracts/BkdLocker.sol#L70-L75
https://github.com/code-423n4/2022-05-backd/tree/main/protocol/contracts/BkdLocker.sol#L302-L322
Users can claim more fees than expected if governance migrates current rewardToken again by fault.
In the migrate() function, there is no requirement newRewardToken != rewardToken.
If this function is called with the same rewardToken parameter, _replacedRewardTokens will contain the current rewardToken also.
Then when the user claims fees, userShares will be added two times for the same token at L302-L305, L314-L317.
Its because curRewardTokenData.userFeeIntegrals[user] is updated at L332 after the userShares calculation for past rewardTokens.
So the user can get paid more fees than he should.
Solidity Visual Developer of VSCode
You need to add this require() at L71.
require(newRewardToken != rewardToken, Error.SAMEASCURRENT);
danhper (Backd) confirmed 
Alex the Entreprenerd (judge) commented:
