Submitted by peakbolt, also found by minhtrng, bin2chen, carrotsmuggler, 0x007, and 0xRobocop (1, 2)
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/2286f80f928f41c8bc189d0657d74ba83286c668/contracts/markets/bigBang/BigBang.sol#L577 
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/2286f80f928f41c8bc189d0657d74ba83286c668/contracts/markets/singularity/SGLLiquidation.sol#L310-L314
In _liquidateUser() for BigBang and Singularity, the liquidator reward is derived by _getCallerReward(). However, it is incorrectly computed using userBorrowPart[user], which is the portion of borrowed amount that does not include the accumulated fees (interests).
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/2286f80f928f41c8bc189d0657d74ba83286c668/contracts/markets/bigBang/BigBang.sol#L576-L580
Using only userBorrowPart[user] is inconsistent with liquidation calculation in Market.sol#L423-L424, which is based on borrowed amount including accumulated fees.
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/2286f80f928f41c8bc189d0657d74ba83286c668/contracts/markets/Market.sol#L423-L424
As the protocol uses a dynamic liquidation incentives mechanism (see below), the liquidator will be given more rewards than required if the liquidator reward is derived by borrowed amount without accumulated fees. That is because the dynamic liquidation incentives mechanism decreases the rewards as it reaches 100% LTV. So computing the liquidator rewards using a lower value (without fees) actually gives liquidator a higher portion of the rewards.
https://github.com/Tapioca-DAO/tapioca-bar-audit/blob/2286f80f928f41c8bc189d0657d74ba83286c668/contracts/markets/Market.sol#L442-L462
The protocol is shortchanged as it gives liquidator more rewards than required.
Change BigBang.sol#L576-L580, SGLLiquidation.sol#L310-L314, Market.sol#L364 from
to
0xRektora (Tapioca) confirmed via duplicate issue 89
