diff --git a/stix2/test/v21/test_malware_analysis.py b/stix2/test/v21/test_malware_analysis.py
index 22f4171..bf4bbe6 100644
--- a/stix2/test/v21/test_malware_analysis.py
+++ b/stix2/test/v21/test_malware_analysis.py
@@ -10,13 +10,9 @@ MALWARE_ANALYSIS_JSON = """{
     "type": "malware-analysis",
     "spec_version": "2.1",
     "id": "malware-analysis--f8afc020-f92f-4906-a971-88ee5882eb46",
+    "created_by_ref": "identity--e0353ed3-991e-4f71-a332-114c2f10b84f",
     "created": "2017-11-28T09:44:58.418Z",
     "modified": "2017-12-31T21:27:49.754Z",
-    "created_by_ref": "identity--e0353ed3-991e-4f71-a332-114c2f10b84f",
-    "labels": [
-        "label1",
-        "label2"
-    ],
     "product": "Acme Malware Analyzer",
     "version": "2.5",
     "host_vm_ref": "software--1bda7336-fe67-469f-a8ca-ab6268b0449b",
@@ -40,7 +36,11 @@ MALWARE_ANALYSIS_JSON = """{
         "file--fc27e371-6c88-4c5c-868a-4dda0e60b167",
         "url--6f7a74cd-8eb2-4b88-a4da-aa878e50ac2e"
     ],
-    "sample_ref": "email-addr--499a32d7-74c1-4276-ace9-725ac933e243"
+    "sample_ref": "email-addr--499a32d7-74c1-4276-ace9-725ac933e243",
+    "labels": [
+        "label1",
+        "label2"
+    ]
 }"""
 
 
diff --git a/stix2/v20/common.py b/stix2/v20/common.py
index f2a371e..720f14f 100644
--- a/stix2/v20/common.py
+++ b/stix2/v20/common.py
@@ -124,11 +124,11 @@ class MarkingDefinition(_STIXBase20, _MarkingsMixin):
         ('id', IDProperty(_type, spec_version='2.0')),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.0')),
         ('created', TimestampProperty(default=lambda: NOW)),
+        ('definition_type', StringProperty(required=True)),
+        ('definition', MarkingProperty(required=True)),
         ('external_references', ListProperty(ExternalReference)),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.0'))),
         ('granular_markings', ListProperty(GranularMarking)),
-        ('definition_type', StringProperty(required=True)),
-        ('definition', MarkingProperty(required=True)),
     ])
 
     def __init__(self, **kwargs):
diff --git a/stix2/v21/common.py b/stix2/v21/common.py
index 1f228af..2980276 100644
--- a/stix2/v21/common.py
+++ b/stix2/v21/common.py
@@ -94,7 +94,7 @@ class LanguageContent(_STIXBase21):
         ('object_modified', TimestampProperty(precision='millisecond')),
         # TODO: 'contents' https://docs.google.com/document/d/1ShNq4c3e1CkfANmD9O--mdZ5H0O_GLnjN28a_yrEaco/edit#heading=h.cfz5hcantmvx
         ('contents', DictionaryProperty(spec_version='2.1', required=True)),
-        ('revoked', BooleanProperty()),
+        ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
         ('confidence', IntegerProperty()),
         ('external_references', ListProperty(ExternalReference)),
@@ -156,12 +156,12 @@ class MarkingDefinition(_STIXBase21, _MarkingsMixin):
         ('id', IDProperty(_type)),
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('external_references', ListProperty(ExternalReference)),
-        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
-        ('granular_markings', ListProperty(GranularMarking)),
         ('definition_type', StringProperty(required=True)),
         ('name', StringProperty()),
         ('definition', MarkingProperty(required=True)),
+        ('external_references', ListProperty(ExternalReference)),
+        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
+        ('granular_markings', ListProperty(GranularMarking)),
     ])
 
     def __init__(self, **kwargs):
diff --git a/stix2/v21/observables.py b/stix2/v21/observables.py
index 55224cd..7919383 100644
--- a/stix2/v21/observables.py
+++ b/stix2/v21/observables.py
@@ -28,6 +28,7 @@ class Artifact(_Observable):
     _type = 'artifact'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('mime_type', StringProperty()),
         ('payload_bin', BinaryProperty()),
@@ -35,11 +36,10 @@ class Artifact(_Observable):
         ('hashes', HashesProperty(spec_version='2.1')),
         ('encryption_algorithm', StringProperty()),
         ('decryption_key', StringProperty()),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["hashes", "payload_bin"]
 
@@ -57,15 +57,15 @@ class AutonomousSystem(_Observable):
     _type = 'autonomous-system'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('number', IntegerProperty(required=True)),
         ('name', StringProperty()),
         ('rir', StringProperty()),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["number"]
 
@@ -78,6 +78,7 @@ class Directory(_Observable):
     _type = 'directory'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('path', StringProperty(required=True)),
         ('path_enc', StringProperty()),
@@ -86,11 +87,10 @@ class Directory(_Observable):
         ('mtime', TimestampProperty()),
         ('atime', TimestampProperty()),
         ('contains_refs', ListProperty(ReferenceProperty(valid_types=['file', 'directory'], spec_version='2.1'))),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["path"]
 
@@ -103,14 +103,14 @@ class DomainName(_Observable):
     _type = 'domain-name'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
         ('resolves_to_refs', ListProperty(ReferenceProperty(valid_types=['ipv4-addr', 'ipv6-addr', 'domain-name'], spec_version='2.1'))),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -123,15 +123,15 @@ class EmailAddress(_Observable):
     _type = 'email-addr'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
         ('display_name', StringProperty()),
         ('belongs_to_ref', ReferenceProperty(valid_types='user-account', spec_version='2.1')),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -161,6 +161,7 @@ class EmailMessage(_Observable):
     _type = 'email-message'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('is_multipart', BooleanProperty(required=True)),
         ('date', TimestampProperty()),
@@ -177,11 +178,10 @@ class EmailMessage(_Observable):
         ('body', StringProperty()),
         ('body_multipart', ListProperty(EmbeddedObjectProperty(type=EmailMIMEComponent))),
         ('raw_email_ref', ReferenceProperty(valid_types='artifact', spec_version='2.1')),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["from_ref", "subject", "body"]
 
@@ -345,6 +345,7 @@ class File(_Observable):
     _type = 'file'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('hashes', HashesProperty(spec_version='2.1')),
         ('size', IntegerProperty(min=0)),
@@ -358,11 +359,10 @@ class File(_Observable):
         ('parent_directory_ref', ReferenceProperty(valid_types='directory', spec_version='2.1')),
         ('contains_refs', ListProperty(ReferenceProperty(valid_types=["SCO"], spec_version='2.1'))),
         ('content_ref', ReferenceProperty(valid_types='artifact', spec_version='2.1')),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["hashes", "name", "parent_directory_ref", "extensions"]
 
@@ -379,15 +379,15 @@ class IPv4Address(_Observable):
     _type = 'ipv4-addr'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
         ('resolves_to_refs', ListProperty(ReferenceProperty(valid_types='mac-addr', spec_version='2.1'))),
         ('belongs_to_refs', ListProperty(ReferenceProperty(valid_types='autonomous-system', spec_version='2.1'))),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -400,15 +400,15 @@ class IPv6Address(_Observable):
     _type = 'ipv6-addr'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
         ('resolves_to_refs', ListProperty(ReferenceProperty(valid_types='mac-addr', spec_version='2.1'))),
         ('belongs_to_refs', ListProperty(ReferenceProperty(valid_types='autonomous-system', spec_version='2.1'))),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -421,13 +421,13 @@ class MACAddress(_Observable):
     _type = 'mac-addr'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -440,13 +440,13 @@ class Mutex(_Observable):
     _type = 'mutex'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('name', StringProperty(required=True)),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["name"]
 
@@ -551,6 +551,7 @@ class NetworkTraffic(_Observable):
     _type = 'network-traffic'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('start', TimestampProperty()),
         ('end', TimestampProperty()),
@@ -569,11 +570,10 @@ class NetworkTraffic(_Observable):
         ('dst_payload_ref', ReferenceProperty(valid_types='artifact', spec_version='2.1')),
         ('encapsulates_refs', ListProperty(ReferenceProperty(valid_types='network-traffic', spec_version='2.1'))),
         ('encapsulated_by_ref', ReferenceProperty(valid_types='network-traffic', spec_version='2.1')),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["start", "src_ref", "dst_ref", "src_port", "dst_port", "protocols"]
 
@@ -673,6 +673,7 @@ class Process(_Observable):
     _type = 'process'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('is_hidden', BooleanProperty()),
         ('pid', IntegerProperty()),
@@ -686,11 +687,10 @@ class Process(_Observable):
         ('image_ref', ReferenceProperty(valid_types='file', spec_version='2.1')),
         ('parent_ref', ReferenceProperty(valid_types='process', spec_version='2.1')),
         ('child_refs', ListProperty(ReferenceProperty(valid_types='process', spec_version='2.1'))),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = []
 
@@ -717,6 +717,7 @@ class Software(_Observable):
     _type = 'software'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('name', StringProperty(required=True)),
         ('cpe', StringProperty()),
@@ -724,11 +725,10 @@ class Software(_Observable):
         ('languages', ListProperty(StringProperty)),
         ('vendor', StringProperty()),
         ('version', StringProperty()),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["name", "cpe", "swid", "vendor", "version"]
 
@@ -741,13 +741,13 @@ class URL(_Observable):
     _type = 'url'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('value', StringProperty(required=True)),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["value"]
 
@@ -774,6 +774,7 @@ class UserAccount(_Observable):
     _type = 'user-account'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('user_id', StringProperty()),
         ('credential', StringProperty()),
@@ -789,11 +790,10 @@ class UserAccount(_Observable):
         ('credential_last_changed', TimestampProperty()),
         ('account_first_login', TimestampProperty()),
         ('account_last_login', TimestampProperty()),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["account_type", "user_id", "account_login"]
 
@@ -835,6 +835,7 @@ class WindowsRegistryKey(_Observable):
     _type = 'windows-registry-key'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('key', StringProperty()),
         ('values', ListProperty(EmbeddedObjectProperty(type=WindowsRegistryValueType))),
@@ -842,11 +843,10 @@ class WindowsRegistryKey(_Observable):
         ('modified_time', TimestampProperty()),
         ('creator_user_ref', ReferenceProperty(valid_types='user-account', spec_version='2.1')),
         ('number_of_subkeys', IntegerProperty()),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["key", "values"]
 
@@ -885,6 +885,7 @@ class X509Certificate(_Observable):
     _type = 'x509-certificate'
     _properties = OrderedDict([
         ('type', TypeProperty(_type, spec_version='2.1')),
+        ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
         ('is_self_signed', BooleanProperty()),
         ('hashes', HashesProperty(spec_version='2.1')),
@@ -899,11 +900,10 @@ class X509Certificate(_Observable):
         ('subject_public_key_modulus', StringProperty()),
         ('subject_public_key_exponent', IntegerProperty()),
         ('x509_v3_extensions', EmbeddedObjectProperty(type=X509V3ExtenstionsType)),
-        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
-        ('spec_version', StringProperty(fixed='2.1')),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),
+        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
     ])
     _id_contributing_properties = ["hashes", "serial_number"]
 
diff --git a/stix2/v21/sdo.py b/stix2/v21/sdo.py
index decbf07..4108001 100644
--- a/stix2/v21/sdo.py
+++ b/stix2/v21/sdo.py
@@ -122,9 +122,13 @@ class Grouping(_DomainObject):
         ('type', TypeProperty(_type, spec_version='2.1')),
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
+        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
+        ('name', StringProperty()),
+        ('description', StringProperty()),
+        ('context', StringProperty(required=True)),
+        ('object_refs', ListProperty(ReferenceProperty(valid_types=["SCO", "SDO", "SRO"], spec_version='2.1'), required=True)),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
         ('confidence', IntegerProperty()),
@@ -132,10 +136,6 @@ class Grouping(_DomainObject):
         ('external_references', ListProperty(ExternalReference)),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
-        ('name', StringProperty()),
-        ('description', StringProperty()),
-        ('context', StringProperty(required=True)),
-        ('object_refs', ListProperty(ReferenceProperty(valid_types=["SCO", "SDO", "SRO"], spec_version='2.1'), required=True)),
     ])
 
 
@@ -240,13 +240,6 @@ class Infrastructure(_DomainObject):
         ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('revoked', BooleanProperty(default=lambda: False)),
-        ('labels', ListProperty(StringProperty)),
-        ('confidence', IntegerProperty()),
-        ('lang', StringProperty()),
-        ('external_references', ListProperty(ExternalReference)),
-        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
-        ('granular_markings', ListProperty(GranularMarking)),
         ('name', StringProperty(required=True)),
         ('description', StringProperty()),
         ('infrastructure_types', ListProperty(StringProperty)),
@@ -254,6 +247,13 @@ class Infrastructure(_DomainObject):
         ('kill_chain_phases', ListProperty(KillChainPhase)),
         ('first_seen', TimestampProperty()),
         ('last_seen', TimestampProperty()),
+        ('revoked', BooleanProperty(default=lambda: False)),
+        ('labels', ListProperty(StringProperty)),
+        ('confidence', IntegerProperty()),
+        ('lang', StringProperty()),
+        ('external_references', ListProperty(ExternalReference)),
+        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
+        ('granular_markings', ListProperty(GranularMarking)),
     ])
 
     def _check_object_constraints(self):
@@ -478,16 +478,9 @@ class MalwareAnalysis(_DomainObject):
         ('type', TypeProperty(_type, spec_version='2.1')),
         ('spec_version', StringProperty(fixed='2.1')),
         ('id', IDProperty(_type, spec_version='2.1')),
+        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
         ('created', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
         ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond', precision_constraint='min')),
-        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
-        ('revoked', BooleanProperty(default=lambda: False)),
-        ('labels', ListProperty(StringProperty)),
-        ('confidence', IntegerProperty()),
-        ('lang', StringProperty()),
-        ('external_references', ListProperty(ExternalReference)),
-        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
-        ('granular_markings', ListProperty(GranularMarking)),
         ('product', StringProperty(required=True)),
         ('version', StringProperty()),
         ('host_vm_ref', ReferenceProperty(valid_types='software', spec_version='2.1')),
@@ -503,7 +496,14 @@ class MalwareAnalysis(_DomainObject):
         ('result_name', StringProperty()),
         ('result', StringProperty()),
         ('analysis_sco_refs', ListProperty(ReferenceProperty(valid_types="SCO", spec_version='2.1'))),
-        ('sample_ref', ReferenceProperty(valid_types="SCO", spec_version="2.1")),
+        ('sample_ref', ReferenceProperty(valid_types="SCO", spec_version='2.1')),
+        ('revoked', BooleanProperty(default=lambda: False)),
+        ('labels', ListProperty(StringProperty)),
+        ('confidence', IntegerProperty()),
+        ('lang', StringProperty()),
+        ('external_references', ListProperty(ExternalReference)),
+        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
+        ('granular_markings', ListProperty(GranularMarking)),
     ])
 
     def _check_object_constraints(self):