Special thanks to external contributors on this release: @erikgrinaker, @guagualvcha, @hsyis, @cosmostuba, @whunmr, @austinabell
Friendly reminder, we have a [bug bounty
program.](https://hackerone.com/tendermint).
### BREAKING CHANGES:
- Go API
- [libs/pubsub] [\#4070](https://github.com/tendermint/tendermint/pull/4070) `Query#(Matches|Conditions)` returns an error.
### IMPROVEMENTS:
- [mempool] [\#4083](https://github.com/tendermint/tendermint/pull/4083) Added TxInfo parameter to CheckTx(), and removed CheckTxWithInfo() (@erikgrinaker)
- [mempool] [\#4057](https://github.com/tendermint/tendermint/issues/4057) Include peer ID when logging rejected txns (@erikgrinaker)
- [tools] [\#4023](https://github.com/tendermint/tendermint/issues/4023) Improved `tm-monitor` formatting of start time and avg tx throughput (@erikgrinaker)
- [p2p] [\#3991](https://github.com/tendermint/tendermint/issues/3991) Log "has been established or dialed" as debug log instead of Error for connected peers (@whunmr)
- [rpc] [\#4077](https://github.com/tendermint/tendermint/pull/4077) Added support for `EXISTS` clause to the Websocket query interface.
- [crypto] Add `RegisterKeyType` to amino to allow external key types registration (@austinabell)
### BUG FIXES:
- [libs/pubsub] [\#4070](https://github.com/tendermint/tendermint/pull/4070) Strip out non-numeric characters when attempting to match numeric values.
- [libs/pubsub] [\#4070](https://github.com/tendermint/tendermint/pull/4070) No longer panic in Query#(Matches|Conditions) preferring to return an error instead.
- [tools] [\#4023](https://github.com/tendermint/tendermint/issues/4023) Refresh `tm-monitor` health when validator count is updated (@erikgrinaker)
- [state] [\#4104](https://github.com/tendermint/tendermint/pull/4104) txindex/kv: Fsync data to disk immediately after receiving it (@guagualvcha)
- [state] [\#4095](https://github.com/tendermint/tendermint/pull/4095) txindex/kv: Return an error if there's one when the user searches for a tx (hash=X) (@hsyis)
- [abci] \#2521 Remove `TotalTxs` and `NumTxs` from `Header`
- [types][\#4151](https://github.com/tendermint/tendermint/pull/4151) Enforce ordering of votes in DuplicateVoteEvidence to be lexicographically sorted on BlockID
- [types][\#4151](https://github.com/tendermint/tendermint/pull/4151) Enforce ordering of votes in DuplicateVoteEvidence to be lexicographically sorted on BlockID
- P2P Protocol
- [p2p][\3668](https://github.com/tendermint/tendermint/pull/3668) Make `SecretConnection` non-malleable
- [mempool][\#4083](https://github.com/tendermint/tendermint/pull/4083) Added TxInfo parameter to CheckTx(), and removed CheckTxWithInfo() (@erikgrinaker)
- [mempool][\#4057](https://github.com/tendermint/tendermint/issues/4057) Include peer ID when logging rejected txns (@erikgrinaker)
- [tools][\#4023](https://github.com/tendermint/tendermint/issues/4023) Improved `tm-monitor` formatting of start time and avg tx throughput (@erikgrinaker)
- [libs/pubsub][\#4070](https://github.com/tendermint/tendermint/pull/4070) No longer panic in `Query#(Matches|Conditions)` preferring to return an error instead.
- [libs/pubsub][\#4070](https://github.com/tendermint/tendermint/pull/4070) Strip out non-numeric characters when attempting to match numeric values.
- [p2p][\#3991](https://github.com/tendermint/tendermint/issues/3991) Log "has been established or dialed" as debug log instead of Error for connected peers (@whunmr)
- [rpc][\#4077](https://github.com/tendermint/tendermint/pull/4077) Added support for `EXISTS` clause to the Websocket query interface.
- [crypto] Add `RegisterKeyType` to amino to allow external key types registration (@austinabell)
- [rpc] \#3188 Added `block_size` to `BlockMeta` this is reflected in `/blockchain`
- [types] \#2521 Add `NumTxs` to `BlockMeta` and `EventDataNewBlockHeader`
- [docs][\#4111](https://github.com/tendermint/tendermint/issues/4111) Replaced dead whitepaper link in README.md
### BUG FIXES:
- [tools][\#4023](https://github.com/tendermint/tendermint/issues/4023) Refresh `tm-monitor` health when validator count is updated (@erikgrinaker)
- [state][\#4104](https://github.com/tendermint/tendermint/pull/4104) txindex/kv: Fsync data to disk immediately after receiving it (@guagualvcha)
- [state][\#4095](https://github.com/tendermint/tendermint/pull/4095) txindex/kv: Return an error if there's one when the user searches for a tx (hash=X) (@hsyis)
- [rpc/lib][\#4051](https://github.com/tendermint/tendermint/pull/4131) Fix RPC client, which was previously resolving https protocol to http (@yenkhoon)
- [rpc][\#4141](https://github.com/tendermint/tendermint/pull/4141) JSONRPCClient: validate that Response.ID matches Request.ID
- [rpc][\#4141](https://github.com/tendermint/tendermint/pull/4141) WSClient: check for unsolicited responses