diff --git a/lib/techniques/blind/inference.py b/lib/techniques/blind/inference.py
index c8dc5399d..7e4868f57 100644
--- a/lib/techniques/blind/inference.py
+++ b/lib/techniques/blind/inference.py
@@ -46,6 +46,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
     finalValue = ""
     asciiTbl = getCharset(charsetType)
     timeBasedCompare = (kb.technique in (PAYLOAD.TECHNIQUE.TIME, PAYLOAD.TECHNIQUE.STACKED))
+    dbms = kb.dbms if kb.dbms else kb.misc.testedDbms
 
     # Set kb.partRun in case "common prediction" feature (a.k.a. "good
     # samaritan") is used
@@ -117,7 +118,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
         hintlock.release()
 
         if hintValue is not None and len(hintValue) >= idx:
-            if kb.dbms in (DBMS.SQLITE, DBMS.ACCESS, DBMS.MAXDB):
+            if dbms in (DBMS.SQLITE, DBMS.ACCESS, DBMS.MAXDB):
                 posValue = hintValue[idx-1]
             else:
                 posValue = ord(hintValue[idx-1])
@@ -169,7 +170,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
             position = (len(charTbl) >> 1)
             posValue = charTbl[position]
 
-            if kb.dbms in (DBMS.SQLITE, DBMS.MAXDB):
+            if dbms in (DBMS.SQLITE, DBMS.MAXDB):
                 pushValue(posValue)
                 posValue = chr(posValue) if posValue < 128 else unichr(posValue)
 
@@ -178,7 +179,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
             queriesCount[0] += 1
             result = Request.queryPage(forgedPayload, timeBasedCompare=timeBasedCompare)
 
-            if kb.dbms in (DBMS.SQLITE, DBMS.MAXDB):
+            if dbms in (DBMS.SQLITE, DBMS.MAXDB):
                 posValue = popValue()
 
             if result:
@@ -465,7 +466,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
                 # check it via equal against the substring-query output
                 if commonPattern is not None:
                     # Substring-query containing equals commonPattern
-                    subquery = queries[kb.dbms].substring.query % (expressionUnescaped, 1, len(commonPattern))
+                    subquery = queries[dbms].substring.query % (expressionUnescaped, 1, len(commonPattern))
                     testValue = unescaper.unescape("'%s'" % commonPattern) if "'" not in commonPattern else unescaper.unescape("%s" % commonPattern, quote=False)
                     query = agent.prefixQuery(safeStringFormat("AND (%s) = %s", (subquery, testValue)))
                     query = agent.suffixQuery(query)
diff --git a/plugins/dbms/access/fingerprint.py b/plugins/dbms/access/fingerprint.py
index d5a01eeb5..c02f66a4d 100644
--- a/plugins/dbms/access/fingerprint.py
+++ b/plugins/dbms/access/fingerprint.py
@@ -22,6 +22,7 @@ from lib.core.data import logger
 from lib.core.enums import DBMS
 from lib.core.session import setDbms
 from lib.core.settings import ACCESS_ALIASES
+from lib.request import inject
 from lib.request.connect import Connect as Request
 
 from plugins.generic.fingerprint import Fingerprint as GenericFingerprint
@@ -40,10 +41,7 @@ class Fingerprint(GenericFingerprint):
             elif kb.dbmsVersion[0] in ("2002-2003", "2007"):
                 table = "MSysAccessStorage"
             if table:
-                query   = agent.prefixQuery("AND EXISTS(SELECT CURDIR() FROM %s)" % table)
-                query   = agent.suffixQuery(query)
-                payload = agent.payload(newValue=query)
-                result  = Request.queryPage(payload)
+                result = inject.checkBooleanExpression("EXISTS(SELECT CURDIR() FROM %s)" % table)
                 retVal = "not sandboxed" if result else "sandboxed"
 
         return retVal
@@ -70,10 +68,7 @@ class Fingerprint(GenericFingerprint):
                     negate = True
                     table = table[1:]
                 randInt = randomInt()
-                query   = agent.prefixQuery("AND EXISTS(SELECT * FROM %s WHERE %d=%d)" % (table, randInt, randInt))
-                query   = agent.suffixQuery(query)
-                payload = agent.payload(newValue=query)
-                result  = Request.queryPage(payload)
+                result = inject.checkBooleanExpression("EXISTS(SELECT * FROM %s WHERE %d=%d)" % (table, randInt, randInt))
                 if result is None:
                     result = False
                 if negate:
@@ -94,13 +89,10 @@ class Fingerprint(GenericFingerprint):
 
         randInt = randomInt()
         randStr = randomStr()
-        query   = agent.prefixQuery("AND EXISTS(SELECT * FROM %s.%s WHERE %d=%d)" % (randStr, randStr, randInt, randInt))
-        query   = agent.suffixQuery(query)
-        payload = agent.payload(newValue=query)
-        page  = Request.queryPage(payload, content=True)
+        _ = inject.checkBooleanExpression("EXISTS(SELECT * FROM %s.%s WHERE %d=%d)" % (randStr, randStr, randInt, randInt))
 
         if wasLastRequestDBMSError():
-            match = re.search("Could not find file\s+'([^']+?)'", page[0])
+            match = re.search("Could not find file\s+'([^']+?)'", kb.lastErrorPage[1])
 
             if match:
                 retVal = match.group(1).rstrip("%s.mdb" % randStr)
@@ -161,15 +153,13 @@ class Fingerprint(GenericFingerprint):
         logMsg = "testing Microsoft Access"
         logger.info(logMsg)
 
-        payload = agent.fullPayload("AND VAL(CVAR(1))=1")
-        result  = Request.queryPage(payload)
+        result = inject.checkBooleanExpression("VAL(CVAR(1))=1")
 
         if result:
             logMsg = "confirming Microsoft Access"
             logger.info(logMsg)
 
-            payload = agent.fullPayload("AND IIF(ATN(2)>0,1,0) BETWEEN 2 AND 0")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("IIF(ATN(2)>0,1,0) BETWEEN 2 AND 0")
 
             if not result:
                 warnMsg = "the back-end DBMS is not Microsoft Access"
diff --git a/plugins/dbms/firebird/fingerprint.py b/plugins/dbms/firebird/fingerprint.py
index f9ce93916..d46446a45 100644
--- a/plugins/dbms/firebird/fingerprint.py
+++ b/plugins/dbms/firebird/fingerprint.py
@@ -22,6 +22,7 @@ from lib.core.data import logger
 from lib.core.enums import DBMS
 from lib.core.session import setDbms
 from lib.core.settings import FIREBIRD_ALIASES
+from lib.request import inject
 from lib.request.connect import Connect as Request
 
 from plugins.generic.fingerprint import Fingerprint as GenericFingerprint
@@ -72,18 +73,17 @@ class Fingerprint(GenericFingerprint):
     def __sysTablesCheck(self):
         retVal = None
         table = (
-                    ("1.0", ["AND EXISTS(SELECT CURRENT_USER FROM RDB$DATABASE)"]),
-                    ("1.5", ["AND NULLIF(%d,%d) IS NULL", "AND EXISTS(SELECT CURRENT_TRANSACTION FROM RDB$DATABASE)"]),
-                    ("2.0", ["AND EXISTS(SELECT CURRENT_TIME(0) FROM RDB$DATABASE)", "AND BIT_LENGTH(%d)>0", "AND CHAR_LENGTH(%d)>0"]),
-                    ("2.1", ["AND BIN_XOR(%d,%d)=0", "AND PI()>0.%d", "AND RAND()<1.%d", "AND FLOOR(1.%d)>=0"])
+                    ("1.0", ["EXISTS(SELECT CURRENT_USER FROM RDB$DATABASE)"]),
+                    ("1.5", ["NULLIF(%d,%d) IS NULL", "EXISTS(SELECT CURRENT_TRANSACTION FROM RDB$DATABASE)"]),
+                    ("2.0", ["EXISTS(SELECT CURRENT_TIME(0) FROM RDB$DATABASE)", "BIT_LENGTH(%d)>0", "CHAR_LENGTH(%d)>0"]),
+                    ("2.1", ["BIN_XOR(%d,%d)=0", "PI()>0.%d", "RAND()<1.%d", "FLOOR(1.%d)>=0"])
                  )
 
         for i in xrange(len(table)):
             version, checks = table[i]
             failed = False
             check = checks[randomRange(0,len(checks)-1)].replace("%d", getUnicode(randomRange(1,100)))
-            payload = agent.fullPayload(check)
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression(check)
             if result:
                 retVal = version
             else:
@@ -97,8 +97,7 @@ class Fingerprint(GenericFingerprint):
     def __dialectCheck(self):
         retVal = None
         if kb.dbms:
-            payload = agent.fullPayload("AND EXISTS(SELECT CURRENT_DATE FROM RDB$DATABASE)")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("EXISTS(SELECT CURRENT_DATE FROM RDB$DATABASE)")
             retVal = "dialect 3" if result else "dialect 1"
         return retVal
 
@@ -115,16 +114,13 @@ class Fingerprint(GenericFingerprint):
         logger.info(logMsg)
 
         randInt = randomInt()
-
-        payload = agent.fullPayload("AND EXISTS(SELECT * FROM RDB$DATABASE WHERE %d=%d)" % (randInt, randInt))
-        result  = Request.queryPage(payload)
+        result = inject.checkBooleanExpression("EXISTS(SELECT * FROM RDB$DATABASE WHERE %d=%d)" % (randInt, randInt))
 
         if result:
             logMsg = "confirming Firebird"
             logger.info(logMsg)
 
-            payload = agent.fullPayload("AND EXISTS(SELECT CURRENT_USER FROM RDB$DATABASE)")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("EXISTS(SELECT CURRENT_USER FROM RDB$DATABASE)")
 
             if not result:
                 warnMsg = "the back-end DBMS is not Firebird"
diff --git a/plugins/dbms/maxdb/fingerprint.py b/plugins/dbms/maxdb/fingerprint.py
index 9bc89bfc1..e053a7073 100644
--- a/plugins/dbms/maxdb/fingerprint.py
+++ b/plugins/dbms/maxdb/fingerprint.py
@@ -22,6 +22,7 @@ from lib.core.data import logger
 from lib.core.enums import DBMS
 from lib.core.session import setDbms
 from lib.core.settings import MAXDB_ALIASES
+from lib.request import inject
 from lib.request.connect import Connect as Request
 
 from plugins.generic.fingerprint import Fingerprint as GenericFingerprint
@@ -48,19 +49,13 @@ class Fingerprint(GenericFingerprint):
         minor, major = None, None
 
         for version in [6, 7]:
-            query   = agent.prefixQuery("AND (SELECT MAJORVERSION FROM SYSINFO.VERSION)=%d" % version)
-            query   = agent.suffixQuery(query)
-            payload = agent.payload(newValue=query)
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("(SELECT MAJORVERSION FROM SYSINFO.VERSION)=%d" % version)
 
             if result:
                 major = version
 
         for version in xrange(0, 10):
-            query   = agent.prefixQuery("AND (SELECT MINORVERSION FROM SYSINFO.VERSION)=%d" % version)
-            query   = agent.suffixQuery(query)
-            payload = agent.payload(newValue=query)
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("(SELECT MINORVERSION FROM SYSINFO.VERSION)=%d" % version)
 
             if result:
                 minor = version
@@ -117,16 +112,13 @@ class Fingerprint(GenericFingerprint):
         logger.info(logMsg)
 
         randInt = randomInt()
-
-        payload = agent.fullPayload("AND NOROUND(%d)=%d" % (randInt, randInt))
-        result  = Request.queryPage(payload)
+        result = inject.checkBooleanExpression("NOROUND(%d)=%d" % (randInt, randInt))
 
         if result:
             logMsg = "confirming SAP MaxDB"
             logger.info(logMsg)
 
-            payload = agent.fullPayload("AND MAPCHAR(NULL,1,DEFAULTMAP) IS NULL")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("MAPCHAR(NULL,1,DEFAULTMAP) IS NULL")
 
             if not result:
                 warnMsg = "the back-end DBMS is not SAP MaxDB"
diff --git a/plugins/dbms/sqlite/fingerprint.py b/plugins/dbms/sqlite/fingerprint.py
index 8f36a6787..567793620 100644
--- a/plugins/dbms/sqlite/fingerprint.py
+++ b/plugins/dbms/sqlite/fingerprint.py
@@ -80,15 +80,13 @@ class Fingerprint(GenericFingerprint):
         logMsg = "testing SQLite"
         logger.info(logMsg)
 
-        payload = agent.fullPayload("AND LAST_INSERT_ROWID()=LAST_INSERT_ROWID()")
-        result  = Request.queryPage(payload)
+        result = inject.checkBooleanExpression("LAST_INSERT_ROWID()=LAST_INSERT_ROWID()")
 
         if result:
             logMsg = "confirming SQLite"
             logger.info(logMsg)
 
-            payload = agent.fullPayload("AND SQLITE_VERSION()=SQLITE_VERSION()")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("SQLITE_VERSION()=SQLITE_VERSION()")
 
             if not result:
                 warnMsg = "the back-end DBMS is not SQLite"
diff --git a/plugins/dbms/sybase/fingerprint.py b/plugins/dbms/sybase/fingerprint.py
index 913d0b7ba..8b87e799a 100644
--- a/plugins/dbms/sybase/fingerprint.py
+++ b/plugins/dbms/sybase/fingerprint.py
@@ -81,15 +81,13 @@ class Fingerprint(GenericFingerprint):
         if conf.direct:
             result = True
         else:
-            payload = agent.fullPayload("AND tempdb_id()=tempdb_id()")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("tempdb_id()=tempdb_id()")
 
         if result:
             logMsg = "confirming Sybase"
             logger.info(logMsg)
 
-            payload = agent.fullPayload("AND suser_id()=suser_id()")
-            result  = Request.queryPage(payload)
+            result = inject.checkBooleanExpression("suser_id()=suser_id()")
 
             if not result:
                 warnMsg = "the back-end DBMS is not Sybase"
@@ -105,10 +103,7 @@ class Fingerprint(GenericFingerprint):
                 return True
 
             for version in range(12, 16):
-                randInt = randomInt()
-                query   = "AND @@VERSION_NUMBER/1000=%d" % version
-                payload = agent.fullPayload(query)
-                result  = Request.queryPage(payload)
+                result = inject.checkBooleanExpression("@@VERSION_NUMBER/1000=%d" % version)
                 if result:
                     kb.dbmsVersion = ["%d" % version]
                     break