Submitted by 0x52, also found by DimitarDimitrov
Potentially inconsistent currency conversions.
addFeedFor requires that a price feed for the _currency _base doesnt exist when adding a new price feed but doesnt check if the inverse already exists. This means that two different oracles (potentially with different prices) could be used for _currency -> _base vs. _base -> _currency. Different prices would lead to inconsistent between conversion ratios depending on the direction of the conversion.
Change L115 to:
if (feedFor\[\_currency]\[\_base] != IJBPriceFeed(address(0)) || feedFor\[\_base]\[\_currency] != IJBPriceFeed(address(0))) revert PRICE_FEED_ALREADY_EXISTS()
mejango (Juicebox) confirmed 
mejango (Juicebox) resolved:
berndartmueller (warden) reviewed mitigation:
