Many contemporary blockchains are greatly dependent on the Proof-of-Stake (PoS) consensus protocol. Among these, Cosmos is a fairly new blockchain system that stands out as a prominent PoS example thanks to its ecosystem designed to facilitate interoperability between different blockchains through the Inter-Blockchain Communication protocol. Cosmos consensus protocol is called CosmosBFT and is based on the definition of rounds for consensus on blocks. The agreement has to be made by special users, namely validators, chosen among the participants with the highest bonded stakes. This paper investigates the potential new attacks that these design features can introduce. First, we show that the current state of nearly every network in the Cosmos ecosystem is prone to the unbalanced distribution of voting power (VP) of validators, as it is skewed towards a small group of already top-ranked ones. Secondly, we introduce a base model reflecting the standard execution of the consensus protocol of the Cosmos ecosystem. Then, we propose two case studies to assess the effect of network performance due to (i) colluded behavior of the highest-ranked validators and (ii) partial absence of the committee members. Our results suggest that a set of validators holding one-third of the total VP (also known as a superminority), either colluded or simultaneously unavailable, is able to drastically reduce the network effectiveness of producing blocks, thereby damaging honest network participants and network security.
