diff --git a/DigitalNote_config.pri b/DigitalNote_config.pri
index ac18fe89..036e89e6 100644
--- a/DigitalNote_config.pri
+++ b/DigitalNote_config.pri
@@ -1,7 +1,7 @@
 DIGITALNOTE_VERSION_MAJOR = 2
 DIGITALNOTE_VERSION_MINOR = 0
 DIGITALNOTE_VERSION_REVISION = 0
-DIGITALNOTE_VERSION_BUILD = 3
+DIGITALNOTE_VERSION_BUILD = 4
 
 DIGITALNOTE_LIB_LEVELDB_DIR = $${DIGITALNOTE_PATH}/src/leveldb
 DIGITALNOTE_LIB_LEVELDB_NEW_DIR = $${DIGITALNOTE_PATH}/src/leveldb-2.11
diff --git a/src/clientversion.h b/src/clientversion.h
index d8d2ecfe..6d295161 100644
--- a/src/clientversion.h
+++ b/src/clientversion.h
@@ -9,7 +9,7 @@
 #define CLIENT_VERSION_MAJOR       2
 #define CLIENT_VERSION_MINOR       0
 #define CLIENT_VERSION_REVISION    0
-#define CLIENT_VERSION_BUILD       3
+#define CLIENT_VERSION_BUILD       4
 
 // Set to true for release, false for prerelease or test build
 #define CLIENT_VERSION_IS_RELEASE  true
diff --git a/src/ctransaction.cpp b/src/ctransaction.cpp
index 25ec50a5..8611db07 100755
--- a/src/ctransaction.cpp
+++ b/src/ctransaction.cpp
@@ -19,6 +19,7 @@
 #include "util.h"
 #include "cautofile.h"
 #include "cdatastream.h"
+#include "checkpoints.h"
 
 #include "ctransaction.h"
 
@@ -494,7 +495,7 @@ bool CTransaction::ConnectInputs(CTxDB& txdb, MapPrevTx inputs, std::map<uint256
                 // Skip ECDSA signature verification when connecting blocks (fBlock=true)
                 // before the last blockchain checkpoint. This is safe because block merkle hashes are
                 // still computed and checked, and any change will be caught at the next checkpoint.
-                if (!(fBlock && !IsInitialBlockDownload()))
+                if (!(fBlock && (nBestHeight < Checkpoints::GetTotalBlocksEstimate())))
                 {
                     // Verify signature
                     if (!VerifySignature(txPrev, *this, i, flags, 0))
diff --git a/src/script.cpp b/src/script.cpp
index 70fad0fc..1adaf7fc 100644
--- a/src/script.cpp
+++ b/src/script.cpp
@@ -3843,6 +3843,13 @@ bool SignSignature(const CKeyStore &keystore, const CTransaction& txFrom, CTrans
 
 bool VerifySignature(const CTransaction& txFrom, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType)
 {
+	std::string _txFrom, _txTo;
+	
+	_txFrom = txFrom.GetHash().ToString();
+	_txTo = txTo.GetHash().ToString();
+	
+	LogPrintf("VerifySignature from %s to %s\n", _txFrom.c_str(), _txTo.c_str());
+	
     assert(nIn < txTo.vin.size());
 	
     const CTxIn& txin = txTo.vin[nIn];
@@ -3859,6 +3866,29 @@ bool VerifySignature(const CTransaction& txFrom, const CTransaction& txTo, unsig
         return false;
 	}
 	
+	/*
+		Exploit happpend on 31st Aug 2021 17:17:26
+		
+		Reference:
+			https://xdn-explorer.com/block/00000000000371f620dba8ef1576407b558686d8b00ca275c3debbfaee6a3db8
+	*/
+	if(
+		(
+			(
+				_txFrom == "81140f106083298143e0e0bd044705b83a891bf2072721dfa43f7237be5931fb" ||
+				_txFrom == "164a0151731efc1536fd75e7d5c4a61e17ef67df1d0f4649b3689d604a41a955"
+			) &&
+			_txTo == "2a639be55df3d7789c73e05aab30edce8fc867d1aae76728e2d59dd2c19b39ab"
+		) ||
+		(
+			_txFrom == "2a639be55df3d7789c73e05aab30edce8fc867d1aae76728e2d59dd2c19b39ab" &&
+			_txTo == "adb24c4a4f50bf848ded522fad8de1546bcc16f1ae838a5b51888bcd753dd25b"
+		)
+	)
+	{
+		return true;
+	}
+	
     return VerifyScript(txin.scriptSig, txout.scriptPubKey, txTo, nIn, flags, nHashType);
 }
 
diff --git a/src/version.h b/src/version.h
index 6aaf7a04..271627d0 100644
--- a/src/version.h
+++ b/src/version.h
@@ -30,13 +30,13 @@ static const int DATABASE_VERSION = 70509;
 //
 // network protocol versioning
 //
-static const int PROTOCOL_VERSION = 62051;
+static const int PROTOCOL_VERSION = 62052;
 
 // intial proto version, to be increased after version/verack negotiation
 static const int INIT_PROTO_VERSION = 209;
 
 // disconnect from peers older than this proto version
-static const int MIN_PEER_PROTO_VERSION = 62049;
+static const int MIN_PEER_PROTO_VERSION = 62052;
 
 // minimum peer version accepted by MNenginePool
 static const int MIN_POOL_PEER_PROTO_VERSION = 62050;
@@ -45,8 +45,8 @@ static const int MIN_INSTANTX_PROTO_VERSION = 62050;
 //! minimum peer version that can receive masternode payments
 // V1 - Last protocol version before update
 // V2 - Newest protocol version
-static const int MIN_MASTERNODE_PAYMENT_PROTO_VERSION_1 = 62050;
-static const int MIN_MASTERNODE_PAYMENT_PROTO_VERSION_2 = 62050;
+static const int MIN_MASTERNODE_PAYMENT_PROTO_VERSION_1 = 62051;
+static const int MIN_MASTERNODE_PAYMENT_PROTO_VERSION_2 = 62051;
 
 // nTime field added to CAddress, starting with this version;
 // if possible, avoid requesting addresses nodes older than this
@@ -54,7 +54,7 @@ static const int CADDR_TIME_VERSION = 31402;
 
 // only request blocks from nodes outside this range of versions
 static const int NOBLKS_VERSION_START = 0;
-static const int NOBLKS_VERSION_END = 62050;
+static const int NOBLKS_VERSION_END = 62051;
 
 // hard cutoff time for legacy network connections
 static const int64_t HRD_LEGACY_CUTOFF = 9993058800; // OFF (NOT TOGGLED)