update changelog for v0.42.4 (#9083)

* update changelog for v0.42.4

* Update RELEASE_NOTES.md

* Update CHANGELOG.md

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

* Update CHANGELOG.md

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

* Update RELEASE_NOTES.md

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

* Update CHANGELOG.md

Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

Co-authored-by: Alessio Treglia <alessio@tendermint.com>
Co-authored-by: Barrie Byron <barrie.byron@tendermint.com>

CHANGELOG.md

@@ -34,11 +34,20 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 # Changelog
 
-## [Unreleased]
+## [v0.42.4](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.42.4) - 2021-04-08
+
+### Client Breaking Changes
+
+* [\#9026](https://github.com/cosmos/cosmos-sdk/pull/9026) By default, the `tx sign` and `tx sign-batch` CLI commands use SIGN_MODE_DIRECT to sign transactions for local pubkeys. For multisigs and ledger keys, the default LEGACY_AMINO_JSON is used.
 
 ### Bug Fixes
 
 * (gRPC) [\#9015](https://github.com/cosmos/cosmos-sdk/pull/9015) Fix invalid status code when accessing gRPC endpoints.
+* [\#9026](https://github.com/cosmos/cosmos-sdk/pull/9026) Fixed the bug that caused the `gentx` command to fail for Ledger keys.
+
+### Improvements
+
+* [\#9081](https://github.com/cosmos/cosmos-sdk/pull/9081) Upgrade Tendermint to v0.34.9 that includes a security issue fix for Tendermint light clients.
 
 ## [v0.42.3](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.42.3) - 2021-03-24
 

RELEASE_NOTES.md

@@ -1,3 +1,5 @@
-# Cosmos SDK v0.42.3 "Stargate" Release Notes
+# Cosmos SDK v0.42.4 "Stargate" Release Notes
 
-This release fixes a security vulnerability identified in x/bank.
+This release includes an important Tendermint update that fixes a security issue with Tendermint light clients. For more information, see [Tendermint v0.34.9 release notes](https://github.com/tendermint/tendermint/blob/v0.34.9/CHANGELOG.md#v0.34.9).
+
+See the [Cosmos SDK v0.42.4 milestone](https://github.com/cosmos/cosmos-sdk/milestone/43?closed=1) on our issue tracker for further details.