Submitted by shaka, also found by ether_sky
https://github.com/code-423n4/2023-10-badger/blob/f2f2e2cf9965a1020661d179af46cb49e993cb7e/packages/contracts/contracts/PriceFeed.sol#L341 
https://github.com/code-423n4/2023-10-badger/blob/f2f2e2cf9965a1020661d179af46cb49e993cb7e/packages/contracts/contracts/PriceFeed.sol#L231
PriceFeed.sol:fetchPrice() can return different prices in the same transaction when Chainlink price changes over 50% and the fallback oracle is not set.
In the scenario of the fallback oracle not set and the Chainlink oracle working correctly the status is usingChainlinkFallbackUntrusted. If the Chainlink price changes over 50%, the condition of line 340 evaluates to true, so the last good price is returned and the status is set to bothOraclesUntrusted.
However, if the price is requested again and the Chainlink price still returns a price change over 50% from the previous round, having the status set to bothOraclesUntrusted will cause the condition of line 220 to evaluate to true and, given that the fallback oracle is not set and the Chainlink oracle is neither broken nor frozen, the price returned will be the current Chainlink price.
A difference in the price returned by fetchPrice in the same transaction can be exploited to perform an arbitrage in different ways.
In the case of an increase of over 50% in the Chainlink price, a user can redeem a CDP with the last good price and then open a new CDP with the current Chainlink price, obtaining a collateral surplus.
In the case of a decrease over 50%, a user can open a CDP with the last good price and then redeem it with the current Chainlink price, obtaining a collateral surplus.
In both cases, the collateral surplus is obtained at the expense of the protocol with no risk for the user.
Alex the Entreprenerd (Badger) confirmed, but disagreed with severity and commented:
rayeaster (Badger) commented:
ronnyx2017 (Judge) decreased severity to Medium and commented:
