Venus Prime - SPYBOY's results

Title

Inconsistent State Transition After Burning Prime Tokens

Description

In the prime contract, there is an inconsistency in the state transition of a user's reward index after burning prime tokens. Specifically, when a user burns their prime tokens by calling _burn(), the contract sets the user's rewardIndex for all markets to zero. However, when the same user subsequently claims interest by calling _claimInterest(), the contract resets the rewardIndex to the current market's rewardIndex. This results in an inconsistent state transition.

Here is the sequence of events:

1) User burns prime tokens by calling `_burn()`.
2) `_burn()` sets the user's `rewardIndex` for all markets to zero.
3) Later, the same user calls `_claimInterest()` to claim interest.
4) `_claimInterest()` resets the user's `rewardIndex` to the current market's `rewardIndex`.

The inconsistency arises because, after burning prime tokens, the user's rewardIndex should remain zero until they earn new rewards. However, _claimInterest() incorrectly updates it to the current market's rewardIndex

maybe this issue could be considered as Medium

Impact

This will result in invalid accounting .