Submitted by leastwood, also found by CertoraInc, csanuragjain, Czar102, hickuphh3, kirk-baird, and WatchPug
The updatePool function intends to calculate the accumulated Concur rewards by tracking the number of blocks passed since the last update to correctly determine how many Concur tokens to distribute to each share. The reward distribution has a start and end block which dictates the timeframe by which rewards will be distributed to the underlying pool.
If a pool has not recently updated itself and has reached the  block.number >= endBlock statement in updatePool, then any rewards that it would normally be entitled to prior to reaching endBlock will not be attributed to the pool. Therefore, once rewards are no longer being distributed, pools who had not recently called updatePool before reaching endBlock are at a disadvantage as compared to more active pools.
MasterChef.sol#L135-L154
Ensure that once the block.number >= endBlock statement has been reached, the pool.accConcurPerShare is updated to reflect the number of blocks that have passed up until endBlock. The number of blocks should be equal to endBlock - pool.lastRewardBlock. This will ensure stale pools are not negatively impacted once endBlock has been reached by the contract.
ryuheimat (Concur) confirmed
Alex the Entreprenerd (judge) commented:
