This release includes an important security fix for all non "Cosmos Hub" chains (e.g. any chain that does not use the default cosmos bech32 prefix), and a few performance improvements.
See the Cosmos SDK v0.42.0 milestone on our issue tracker for further details.
The security fix resolves the issue regarding incorrect handling of validators' consensus addresses. Because of this incorrect handling, Cosmos SDK apps that were not using the default cosmos Bech32 address prefix were not able to jail validators that committed misbehaviors such as double signing.
Although the issue does not affect the Cosmos Hub, this issue potentially renders the v0.41 and v0.40 release series unsafe for most chains.
The event emitted by the IBC UpdateClient message now contains the full header. This change makes header tracking easier and improves the handling of misbehaviors.