diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index bc81f59fbe..b98865e301 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -5,6 +5,13 @@ These are notable changes in edx-platform.  This is a rolling list of changes,
 in roughly chronological order, most recent first.  Add your entries at or near
 the top.  Include a label indicating the component affected.
 
+Common: Add feature flags to allow developer use of pure XBlocks
+  - ALLOW_ALL_ADVANCED_COMPONENTS disables the hard-coded list of advanced
+    components in Studio, and allows any xblock to be added as an
+    advanced component in Studio settings
+  - XBLOCK_SELECT_FUNCTION allows the insertion of a custom function
+    to limit loading of XBlocks with (including allowing pure xblocks)
+
 Studio: Add sorting by column to the Files & Uploads page.
 See mongo_indexes.md for new indices that should be added.
 
diff --git a/cms/djangoapps/contentstore/tests/test_crud.py b/cms/djangoapps/contentstore/tests/test_crud.py
index 8fd54ac831..6094c7cf3b 100644
--- a/cms/djangoapps/contentstore/tests/test_crud.py
+++ b/cms/djangoapps/contentstore/tests/test_crud.py
@@ -9,7 +9,8 @@ from xmodule.modulestore.locator import CourseLocator, BlockUsageLocator, LocalI
 from xmodule.modulestore.exceptions import ItemNotFoundError
 from xmodule.html_module import HtmlDescriptor
 from xmodule.modulestore import inheritance
-from xmodule.x_module import XModuleDescriptor
+from xmodule.x_module import prefer_xmodules
+from xblock.core import XBlock
 
 
 class TemplateTests(unittest.TestCase):
@@ -248,9 +249,10 @@ class TemplateTests(unittest.TestCase):
         - 'definition':
         - '_id' (optional): the usage_id of this. Will generate one if not given one.
         """
-        class_ = XModuleDescriptor.load_class(
+        class_ = XBlock.load_class(
             json_data.get('category', json_data.get('location', {}).get('category')),
-            default_class
+            default_class,
+            select=prefer_xmodules
         )
         usage_id = json_data.get('_id', None)
         if not '_inherited_settings' in json_data and parent_xblock is not None:
diff --git a/cms/djangoapps/contentstore/views/component.py b/cms/djangoapps/contentstore/views/component.py
index 0273ccc716..6dd5b6c293 100644
--- a/cms/djangoapps/contentstore/views/component.py
+++ b/cms/djangoapps/contentstore/views/component.py
@@ -14,13 +14,14 @@ from xmodule.modulestore.django import modulestore
 from xmodule.util.date_utils import get_default_time_display
 from xmodule.modulestore.django import loc_mapper
 from xmodule.modulestore.locator import BlockUsageLocator
-from xmodule.x_module import XModuleDescriptor
 
+from xblock.core import XBlock
 from xblock.django.request import webob_to_django_response, django_to_webob_request
 from xblock.exceptions import NoSuchHandlerError
 from xblock.fields import Scope
 from xblock.plugin import PluginMissingError
 from xblock.runtime import Mixologist
+from xmodule.x_module import prefer_xmodules
 
 from lms.lib.xblock.runtime import unquote_slashes
 
@@ -44,12 +45,18 @@ COMPONENT_TYPES = ['discussion', 'html', 'problem', 'video']
 
 OPEN_ENDED_COMPONENT_TYPES = ["combinedopenended", "peergrading"]
 NOTE_COMPONENT_TYPES = ['notes']
-ADVANCED_COMPONENT_TYPES = [
-    'annotatable',
-    'word_cloud',
-    'graphical_slider_tool',
-    'lti',
-] + OPEN_ENDED_COMPONENT_TYPES + NOTE_COMPONENT_TYPES
+
+if settings.FEATURES.get('ALLOW_ALL_ADVANCED_COMPONENTS'):
+    ADVANCED_COMPONENT_TYPES = sorted(set(name for name, class_ in XBlock.load_classes()) - set(COMPONENT_TYPES))
+else:
+
+    ADVANCED_COMPONENT_TYPES = [
+        'annotatable',
+        'word_cloud',
+        'graphical_slider_tool',
+        'lti',
+    ] + OPEN_ENDED_COMPONENT_TYPES + NOTE_COMPONENT_TYPES
+
 ADVANCED_COMPONENT_CATEGORY = 'advanced'
 ADVANCED_COMPONENT_POLICY_KEY = 'advanced_modules'
 
@@ -138,7 +145,7 @@ def _load_mixed_class(category):
     """
     Load an XBlock by category name, and apply all defined mixins
     """
-    component_class = XModuleDescriptor.load_class(category)
+    component_class = XBlock.load_class(category, select=prefer_xmodules)
     mixologist = Mixologist(settings.XBLOCK_MIXINS)
     return mixologist.mix(component_class)
 
diff --git a/cms/djangoapps/contentstore/views/item.py b/cms/djangoapps/contentstore/views/item.py
index 9fa2a56f7f..d6a8ff3abb 100644
--- a/cms/djangoapps/contentstore/views/item.py
+++ b/cms/djangoapps/contentstore/views/item.py
@@ -9,10 +9,17 @@ from xmodule_modifiers import wrap_xblock
 
 from django.core.exceptions import PermissionDenied
 from django.contrib.auth.decorators import login_required
+from django.http import HttpResponseBadRequest
+from django.views.decorators.http import require_http_methods
+
+from xblock.fields import Scope
+from xblock.core import XBlock
 
 from xmodule.modulestore.django import modulestore, loc_mapper
-from xmodule.modulestore.inheritance import own_metadata
 from xmodule.modulestore.exceptions import ItemNotFoundError, InvalidLocationError
+from xmodule.modulestore.inheritance import own_metadata
+from xmodule.modulestore.locator import BlockUsageLocator
+from xmodule.x_module import prefer_xmodules
 
 from util.json_request import expect_json, JsonResponse
 from util.string_utils import str_to_bool
@@ -23,12 +30,6 @@ from ..utils import get_modulestore
 
 from .access import has_access
 from .helpers import _xmodule_recurse
-from xmodule.x_module import XModuleDescriptor
-from django.views.decorators.http import require_http_methods
-from xmodule.modulestore.locator import BlockUsageLocator
-from student.models import CourseEnrollment
-from django.http import HttpResponseBadRequest
-from xblock.fields import Scope
 from preview import handler_prefix, get_preview_html
 from edxmako.shortcuts import render_to_response, render_to_string
 from models.settings.course_grading import CourseGradingModel
@@ -260,7 +261,7 @@ def _create_item(request):
     data = None
     template_id = request.json.get('boilerplate')
     if template_id is not None:
-        clz = XModuleDescriptor.load_class(category)
+        clz = XBlock.load_class(category, select=prefer_xmodules)
         if clz is not None:
             template = clz.get_template(template_id)
             if template is not None:
diff --git a/cms/envs/common.py b/cms/envs/common.py
index d8f187223c..eb7d600c20 100644
--- a/cms/envs/common.py
+++ b/cms/envs/common.py
@@ -31,7 +31,7 @@ from path import path
 from lms.lib.xblock.mixin import LmsBlockMixin
 from cms.lib.xblock.mixin import CmsBlockMixin
 from xmodule.modulestore.inheritance import InheritanceMixin
-from xmodule.x_module import XModuleMixin
+from xmodule.x_module import XModuleMixin, only_xmodules
 from dealer.git import git
 
 ############################ FEATURE CONFIGURATION #############################
@@ -62,6 +62,10 @@ FEATURES = {
     # If set to True, new Studio users won't be able to author courses unless
     # edX has explicitly added them to the course creator group.
     'ENABLE_CREATOR_GROUP': False,
+
+    # If set to True, Studio won't restrict the set of advanced components
+    # to just those pre-approved by edX
+    'ALLOW_ALL_ADVANCED_COMPONENTS': False,
 }
 ENABLE_JASMINE = False
 
@@ -178,6 +182,15 @@ MIDDLEWARE_CLASSES = (
 # once the responsibility of XBlock creation is moved out of modulestore - cpennington
 XBLOCK_MIXINS = (LmsBlockMixin, CmsBlockMixin, InheritanceMixin, XModuleMixin)
 
+# Only allow XModules in Studio
+XBLOCK_SELECT_FUNCTION = only_xmodules
+
+# Use the following lines to allow any xblock in Studio,
+# either by uncommenting them here, or adding them to your private.py
+# You should also enable the ALLOW_ALL_ADVANCED_COMPONENTS feature flag, so that
+# xblocks can be added via advanced settings
+# from xmodule.x_module import prefer_xmodules
+# XBLOCK_SELECT_FUNCTION = prefer_xmodules
 
 ############################ SIGNAL HANDLERS ################################
 # This is imported to register the exception signal handling that logs exceptions
diff --git a/common/lib/xmodule/xmodule/modulestore/__init__.py b/common/lib/xmodule/xmodule/modulestore/__init__.py
index ebec6d6ee8..e3386608dc 100644
--- a/common/lib/xmodule/xmodule/modulestore/__init__.py
+++ b/common/lib/xmodule/xmodule/modulestore/__init__.py
@@ -430,7 +430,7 @@ class ModuleStoreReadBase(ModuleStoreRead):
         self,
         doc_store_config=None,  # ignore if passed up
         metadata_inheritance_cache_subsystem=None, request_cache=None,
-        modulestore_update_signal=None, xblock_mixins=(),
+        modulestore_update_signal=None, xblock_mixins=(), xblock_select=None,
         # temporary parms to enable backward compatibility. remove once all envs migrated
         db=None, collection=None, host=None, port=None, tz_aware=True, user=None, password=None
     ):
@@ -442,6 +442,7 @@ class ModuleStoreReadBase(ModuleStoreRead):
         self.modulestore_update_signal = modulestore_update_signal
         self.request_cache = request_cache
         self.xblock_mixins = xblock_mixins
+        self.xblock_select = xblock_select
 
     def _get_errorlog(self, location):
         """
diff --git a/common/lib/xmodule/xmodule/modulestore/django.py b/common/lib/xmodule/xmodule/modulestore/django.py
index ef4b9df40a..13e0a2878f 100644
--- a/common/lib/xmodule/xmodule/modulestore/django.py
+++ b/common/lib/xmodule/xmodule/modulestore/django.py
@@ -66,6 +66,7 @@ def create_modulestore_instance(engine, doc_store_config, options):
         request_cache=request_cache,
         modulestore_update_signal=Signal(providing_args=['modulestore', 'course_id', 'location']),
         xblock_mixins=getattr(settings, 'XBLOCK_MIXINS', ()),
+        xblock_select=getattr(settings, 'XBLOCK_SELECT_FUNCTION', None),
         doc_store_config=doc_store_config,
         **_options
     )
@@ -83,7 +84,7 @@ def get_default_store_name_for_current_request():
 
     # get mapping information which is defined in configurations
     mappings = getattr(settings, 'HOSTNAME_MODULESTORE_DEFAULT_MAPPINGS', None)
-   
+
     # compare hostname against the regex expressions set of mappings
     # which will tell us which store name to use
     if hostname and mappings:
diff --git a/common/lib/xmodule/xmodule/modulestore/mongo/base.py b/common/lib/xmodule/xmodule/modulestore/mongo/base.py
index e13c609ab3..c655800609 100644
--- a/common/lib/xmodule/xmodule/modulestore/mongo/base.py
+++ b/common/lib/xmodule/xmodule/modulestore/mongo/base.py
@@ -25,7 +25,6 @@ from path import path
 from importlib import import_module
 from xmodule.errortracker import null_error_tracker, exc_info_to_str
 from xmodule.mako_module import MakoDescriptorSystem
-from xmodule.x_module import XModuleDescriptor
 from xmodule.error_module import ErrorDescriptor
 from xblock.runtime import DbModel
 from xblock.exceptions import InvalidScopeError
@@ -173,10 +172,8 @@ class CachingDescriptorSystem(MakoDescriptorSystem):
             # load the module and apply the inherited metadata
             try:
                 category = json_data['location']['category']
-                class_ = XModuleDescriptor.load_class(
-                    category,
-                    self.default_class
-                )
+                class_ = self.load_block_type(category)
+
                 definition = json_data.get('definition', {})
                 metadata = json_data.get('metadata', {})
                 for old_name, new_name in getattr(class_, 'metadata_translations', {}).items():
@@ -506,6 +503,7 @@ class MongoModuleStore(ModuleStoreWriteBase):
             render_template=self.render_template,
             cached_metadata=cached_metadata,
             mixins=self.xblock_mixins,
+            select=self.xblock_select,
         )
         return system.load_item(item['location'])
 
@@ -627,8 +625,9 @@ class MongoModuleStore(ModuleStoreWriteBase):
                 render_template=self.render_template,
                 cached_metadata={},
                 mixins=self.xblock_mixins,
+                select=self.xblock_select,
             )
-        xblock_class = XModuleDescriptor.load_class(location.category, self.default_class)
+        xblock_class = system.load_block_type(location.category)
         if definition_data is None:
             if hasattr(xblock_class, 'data') and xblock_class.data.default is not None:
                 definition_data = xblock_class.data.default
diff --git a/common/lib/xmodule/xmodule/modulestore/split_mongo/caching_descriptor_system.py b/common/lib/xmodule/xmodule/modulestore/split_mongo/caching_descriptor_system.py
index f209ceddf7..b755ba691f 100644
--- a/common/lib/xmodule/xmodule/modulestore/split_mongo/caching_descriptor_system.py
+++ b/common/lib/xmodule/xmodule/modulestore/split_mongo/caching_descriptor_system.py
@@ -1,7 +1,6 @@
 import sys
 import logging
 from xmodule.mako_module import MakoDescriptorSystem
-from xmodule.x_module import XModuleDescriptor
 from xmodule.modulestore.locator import BlockUsageLocator, LocalId
 from xmodule.error_module import ErrorDescriptor
 from xmodule.errortracker import exc_info_to_str
@@ -62,10 +61,7 @@ class CachingDescriptorSystem(MakoDescriptorSystem):
             if json_data is None:
                 raise ItemNotFoundError(block_id)
 
-        class_ = XModuleDescriptor.load_class(
-            json_data.get('category'),
-            self.default_class
-        )
+        class_ = self.load_block_type(json_data.get('category'))
         return self.xblock_from_json(class_, block_id, json_data, course_entry_override)
 
     # xblock's runtime does not always pass enough contextual information to figure out
diff --git a/common/lib/xmodule/xmodule/modulestore/split_mongo/split.py b/common/lib/xmodule/xmodule/modulestore/split_mongo/split.py
index 4c1d8b116b..1a92f961ec 100644
--- a/common/lib/xmodule/xmodule/modulestore/split_mongo/split.py
+++ b/common/lib/xmodule/xmodule/modulestore/split_mongo/split.py
@@ -42,7 +42,7 @@ Representation:
         *** 'edited_by': user_id whose edit caused this version of the definition,
         *** 'edited_on': datetime of the change causing this version
         *** 'previous_version': the definition_id of the previous version of this definition
-        *** 'original_version': definition_id of the root of the previous version relation on this 
+        *** 'original_version': definition_id of the root of the previous version relation on this
         definition. Acts as a pseudo-object identifier.
 """
 import threading
@@ -56,7 +56,7 @@ import copy
 from pytz import UTC
 
 from xmodule.errortracker import null_error_tracker
-from xmodule.x_module import XModuleDescriptor
+from xmodule.x_module import XModuleDescriptor, prefer_xmodules
 from xmodule.modulestore.locator import BlockUsageLocator, DefinitionLocator, CourseLocator, VersionTree, LocalId
 from xmodule.modulestore.exceptions import InsufficientSpecificationError, VersionConflictError, DuplicateItemError
 from xmodule.modulestore import inheritance, ModuleStoreWriteBase, Location, SPLIT_MONGO_MODULESTORE_TYPE
@@ -68,6 +68,7 @@ from xblock.fields import Scope
 from xblock.runtime import Mixologist
 from bson.objectid import ObjectId
 from xmodule.modulestore.split_mongo.mongo_connection import MongoConnection
+from xblock.core import XBlock
 
 log = logging.getLogger(__name__)
 #==============================================================================
@@ -184,7 +185,8 @@ class SplitMongoModuleStore(ModuleStoreWriteBase):
                 error_tracker=self.error_tracker,
                 render_template=self.render_template,
                 resources_fs=None,
-                mixins=self.xblock_mixins
+                mixins=self.xblock_mixins,
+                select=self.xblock_select,
             )
             self._add_cache(course_entry['structure']['_id'], system)
             self.cache_items(system, block_ids, depth, lazy)
@@ -1471,7 +1473,7 @@ class SplitMongoModuleStore(ModuleStoreWriteBase):
         """
         if fields is None:
             return {}
-        cls = self.mixologist.mix(XModuleDescriptor.load_class(category))
+        cls = self.mixologist.mix(XBlock.load_class(category, select=prefer_xmodules))
         result = collections.defaultdict(dict)
         for field_name, value in fields.iteritems():
             field = getattr(cls, field_name)
@@ -1581,7 +1583,7 @@ class SplitMongoModuleStore(ModuleStoreWriteBase):
                 destination_block['edit_info']['edited_by'] = user_id
         else:
             destination_block = self._new_block(
-                user_id, new_block['category'], 
+                user_id, new_block['category'],
                 self._filter_blacklist(copy.copy(new_block['fields']), blacklist),
                 new_block['definition'],
                 new_block['edit_info']['update_version']
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/factories.py b/common/lib/xmodule/xmodule/modulestore/tests/factories.py
index 2cbe7e6e22..70b580b69d 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/factories.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/factories.py
@@ -6,7 +6,8 @@ from uuid import uuid4
 from pytz import UTC
 
 from xmodule.modulestore import Location
-from xmodule.x_module import XModuleDescriptor
+from xmodule.x_module import prefer_xmodules
+from xblock.core import XBlock
 
 
 class Dummy(object):
@@ -144,7 +145,7 @@ class ItemFactory(XModuleFactory):
 
         if 'boilerplate' in kwargs:
             template_id = kwargs.pop('boilerplate')
-            clz = XModuleDescriptor.load_class(category)
+            clz = XBlock.load_class(category, select=prefer_xmodules)
             template = clz.get_template(template_id)
             assert template is not None
             metadata.update(template.get('metadata', {}))
diff --git a/common/lib/xmodule/xmodule/modulestore/xml.py b/common/lib/xmodule/xmodule/modulestore/xml.py
index 9d055356fc..02df55569a 100644
--- a/common/lib/xmodule/xmodule/modulestore/xml.py
+++ b/common/lib/xmodule/xmodule/modulestore/xml.py
@@ -17,7 +17,7 @@ from xmodule.error_module import ErrorDescriptor
 from xmodule.errortracker import make_error_tracker, exc_info_to_str
 from xmodule.course_module import CourseDescriptor
 from xmodule.mako_module import MakoDescriptorSystem
-from xmodule.x_module import XMLParsingSystem, XModuleDescriptor
+from xmodule.x_module import XMLParsingSystem, prefer_xmodules
 
 from xmodule.html_module import HtmlDescriptor
 from xblock.core import XBlock
@@ -238,7 +238,7 @@ def create_block_from_xml(xml_data, system, org=None, course=None, default_class
 
     """
     node = etree.fromstring(xml_data)
-    raw_class = XModuleDescriptor.load_class(node.tag, default_class)
+    raw_class = XBlock.load_class(node.tag, default_class, select=prefer_xmodules)
     xblock_class = system.mixologist.mix(raw_class)
 
     # leave next line commented out - useful for low-level debugging
@@ -460,6 +460,7 @@ class XMLModuleStore(ModuleStoreReadBase):
                 load_error_modules=self.load_error_modules,
                 policy=policy,
                 mixins=self.xblock_mixins,
+                select=self.xblock_select,
             )
 
             course_descriptor = system.process_xml(etree.tostring(course_data, encoding='unicode'))
diff --git a/common/lib/xmodule/xmodule/modulestore/xml_importer.py b/common/lib/xmodule/xmodule/modulestore/xml_importer.py
index 744a771e1a..176710bca2 100644
--- a/common/lib/xmodule/xmodule/modulestore/xml_importer.py
+++ b/common/lib/xmodule/xmodule/modulestore/xml_importer.py
@@ -132,6 +132,7 @@ def import_from_xml(
         course_dirs=course_dirs,
         load_error_modules=load_error_modules,
         xblock_mixins=store.xblock_mixins,
+        xblock_select=store.xblock_select,
     )
 
     # NOTE: the XmlModuleStore does not implement get_items()
diff --git a/common/lib/xmodule/xmodule/templates.py b/common/lib/xmodule/xmodule/templates.py
index 8e350bb618..d5d45619f1 100644
--- a/common/lib/xmodule/xmodule/templates.py
+++ b/common/lib/xmodule/xmodule/templates.py
@@ -12,7 +12,7 @@ samples.
 import logging
 
 from collections import defaultdict
-from .x_module import XModuleDescriptor
+from xblock.core import XBlock
 
 log = logging.getLogger(__name__)
 
@@ -23,7 +23,9 @@ def all_templates():
     """
     # TODO use memcache to memoize w/ expiration
     templates = defaultdict(list)
-    for category, descriptor in XModuleDescriptor.load_classes():
+    for category, descriptor in XBlock.load_classes():
+        if not hasattr(descriptor, 'templates'):
+            continue
         templates[category] = descriptor.templates()
 
     return templates
diff --git a/common/lib/xmodule/xmodule/tests/test_import.py b/common/lib/xmodule/xmodule/tests/test_import.py
index 969886345d..3a192318a6 100644
--- a/common/lib/xmodule/xmodule/tests/test_import.py
+++ b/common/lib/xmodule/xmodule/tests/test_import.py
@@ -13,7 +13,7 @@ from xmodule.xml_module import is_pointer_tag
 from xmodule.modulestore import Location
 from xmodule.modulestore.xml import ImportSystem, XMLModuleStore
 from xmodule.modulestore.inheritance import compute_inherited_metadata
-from xmodule.x_module import XModuleMixin
+from xmodule.x_module import XModuleMixin, only_xmodules
 from xmodule.fields import Date
 from xmodule.tests import DATA_DIR
 from xmodule.modulestore.inheritance import InheritanceMixin
@@ -61,7 +61,12 @@ class BaseCourseTestCase(unittest.TestCase):
         """Get a test course by directory name.  If there's more than one, error."""
         print("Importing {0}".format(name))
 
-        modulestore = XMLModuleStore(DATA_DIR, course_dirs=[name], xblock_mixins=(InheritanceMixin,))
+        modulestore = XMLModuleStore(
+            DATA_DIR,
+            course_dirs=[name],
+            xblock_mixins=(InheritanceMixin,),
+            xblock_select=only_xmodules,
+        )
         courses = modulestore.get_courses()
         self.assertEquals(len(courses), 1)
         return courses[0]
diff --git a/common/lib/xmodule/xmodule/tests/xml/__init__.py b/common/lib/xmodule/xmodule/tests/xml/__init__.py
index 93aa582cde..624a61d13f 100644
--- a/common/lib/xmodule/xmodule/tests/xml/__init__.py
+++ b/common/lib/xmodule/xmodule/tests/xml/__init__.py
@@ -25,6 +25,7 @@ class InMemorySystem(XMLParsingSystem, MakoDescriptorSystem):  # pylint: disable
             error_tracker=Mock(),
             resources_fs=xml_import_data.filesystem,
             mixins=xml_import_data.xblock_mixins,
+            select=xml_import_data.xblock_select,
             render_template=lambda template, context: pprint.pformat((template, context))
         )
 
diff --git a/common/lib/xmodule/xmodule/tests/xml/factories.py b/common/lib/xmodule/xmodule/tests/xml/factories.py
index 168dcd579b..29857f2571 100644
--- a/common/lib/xmodule/xmodule/tests/xml/factories.py
+++ b/common/lib/xmodule/xmodule/tests/xml/factories.py
@@ -9,6 +9,7 @@ from factory import Factory, lazy_attribute, post_generation, Sequence
 from lxml import etree
 
 from xmodule.modulestore.inheritance import InheritanceMixin
+from xmodule.x_module import only_xmodules
 
 
 class XmlImportData(object):
@@ -19,7 +20,7 @@ class XmlImportData(object):
     def __init__(self, xml_node, xml=None, org=None, course=None,
                  default_class=None, policy=None,
                  filesystem=None, parent=None,
-                 xblock_mixins=()):
+                 xblock_mixins=(), xblock_select=None):
 
         self._xml_node = xml_node
         self._xml_string = xml
@@ -28,6 +29,7 @@ class XmlImportData(object):
         self.default_class = default_class
         self.filesystem = filesystem
         self.xblock_mixins = xblock_mixins
+        self.xblock_select = xblock_select
         self.parent = parent
 
         if policy is None:
@@ -47,7 +49,8 @@ class XmlImportData(object):
         return u"XmlImportData{!r}".format((
             self._xml_node, self._xml_string, self.org,
             self.course, self.default_class, self.policy,
-            self.filesystem, self.parent, self.xblock_mixins
+            self.filesystem, self.parent, self.xblock_mixins,
+            self.xblock_select,
         ))
 
 
@@ -65,6 +68,7 @@ class XmlImportFactory(Factory):
 
     filesystem = MemoryFS()
     xblock_mixins = (InheritanceMixin,)
+    xblock_select = only_xmodules
     url_name = Sequence(str)
     attribs = {}
     policy = {}
diff --git a/common/lib/xmodule/xmodule/x_module.py b/common/lib/xmodule/xmodule/x_module.py
index bf5fb18d66..ffc6862115 100644
--- a/common/lib/xmodule/xmodule/x_module.py
+++ b/common/lib/xmodule/xmodule/x_module.py
@@ -15,9 +15,10 @@ from xmodule.modulestore.exceptions import ItemNotFoundError, InsufficientSpecif
 
 from xblock.core import XBlock
 from xblock.fields import Scope, Integer, Float, List, XBlockMixin, String
-from xmodule.fields import RelativeTime
 from xblock.fragment import Fragment
+from xblock.plugin import default_select
 from xblock.runtime import Runtime
+from xmodule.fields import RelativeTime
 from xmodule.errortracker import exc_info_to_str
 from xmodule.modulestore.locator import BlockUsageLocator
 
@@ -564,6 +565,22 @@ class ResourceTemplates(object):
             return None
 
 
+def prefer_xmodules(identifier, entry_points):
+    """Prefer entry_points from the xmodule package"""
+    from_xmodule = [entry_point for entry_point in entry_points if entry_point.dist.key == 'xmodule']
+    if from_xmodule:
+        return default_select(identifier, from_xmodule)
+    else:
+        return default_select(identifier, entry_points)
+
+
+def only_xmodules(identifier, entry_points):
+    """Only use entry_points that are supplied by the xmodule package"""
+    from_xmodule = [entry_point for entry_point in entry_points if entry_point.dist.key == 'xmodule']
+
+    return default_select(identifier, from_xmodule)
+
+
 @XBlock.needs("i18n")
 class XModuleDescriptor(XModuleMixin, HTMLSnippet, ResourceTemplates, XBlock):
     """
diff --git a/lms/djangoapps/courseware/access.py b/lms/djangoapps/courseware/access.py
index acb850ff56..fa67a920d3 100644
--- a/lms/djangoapps/courseware/access.py
+++ b/lms/djangoapps/courseware/access.py
@@ -11,7 +11,9 @@ from django.contrib.auth.models import Group, AnonymousUser
 from xmodule.course_module import CourseDescriptor
 from xmodule.error_module import ErrorDescriptor
 from xmodule.modulestore import Location
-from xmodule.x_module import XModule, XModuleDescriptor
+from xmodule.x_module import XModule
+
+from xblock.core import XBlock
 
 from student.models import CourseEnrollmentAllowed
 from external_auth.models import ExternalAuthMap
@@ -74,13 +76,13 @@ def has_access(user, obj, action, course_context=None):
     if isinstance(obj, ErrorDescriptor):
         return _has_access_error_desc(user, obj, action, course_context)
 
-    # NOTE: any descriptor access checkers need to go above this
-    if isinstance(obj, XModuleDescriptor):
-        return _has_access_descriptor(user, obj, action, course_context)
-
     if isinstance(obj, XModule):
         return _has_access_xmodule(user, obj, action, course_context)
 
+    # NOTE: any descriptor access checkers need to go above this
+    if isinstance(obj, XBlock):
+        return _has_access_descriptor(user, obj, action, course_context)
+
     if isinstance(obj, Location):
         return _has_access_location(user, obj, action, course_context)
 
@@ -338,7 +340,7 @@ def _dispatch(table, action, user, obj):
         debug("%s user %s, object %s, action %s",
               'ALLOWED' if result else 'DENIED',
               user,
-              obj.location.url() if isinstance(obj, XModuleDescriptor) else str(obj)[:60],
+              obj.location.url() if isinstance(obj, XBlock) else str(obj)[:60],
               action)
         return result
 
diff --git a/lms/djangoapps/courseware/module_render.py b/lms/djangoapps/courseware/module_render.py
index 5b8168d204..377a238ee6 100644
--- a/lms/djangoapps/courseware/module_render.py
+++ b/lms/djangoapps/courseware/module_render.py
@@ -27,6 +27,7 @@ from psychometrics.psychoanalyze import make_psychometrics_data_update_handler
 from student.models import anonymous_id_for_user, user_by_anonymous_id
 from util.json_request import JsonResponse
 from util.sandboxing import can_execute_unsafe_code
+from xblock.core import XBlock
 from xblock.fields import Scope
 from xblock.runtime import DbModel, KeyValueStore
 from xblock.exceptions import NoSuchHandlerError
@@ -38,6 +39,7 @@ from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.exceptions import ItemNotFoundError
 from xmodule_modifiers import replace_course_urls, replace_jump_to_id_urls, replace_static_urls, add_histogram, wrap_xblock
 from xmodule.lti_module import LTIModule
+from xmodule.x_module import XModuleDescriptor
 
 
 log = logging.getLogger(__name__)
@@ -373,7 +375,9 @@ def get_module_for_descriptor_internal(user, descriptor, field_data_cache, cours
     # while giving selected modules a per-course anonymized id.
     # As we have the time to manually test more modules, we can add to the list
     # of modules that get the per-course anonymized id.
-    if issubclass(getattr(descriptor, 'module_class', None), LTIModule):
+    is_pure_xblock = isinstance(descriptor, XBlock) and not isinstance(descriptor, XModuleDescriptor)
+    is_lti_module = not is_pure_xblock and issubclass(descriptor.module_class, LTIModule)
+    if is_pure_xblock or is_lti_module:
         anonymous_student_id = anonymous_id_for_user(user, course_id)
     else:
         anonymous_student_id = anonymous_id_for_user(user, '')
diff --git a/lms/djangoapps/debug/management/commands/dump_xml_courses.py b/lms/djangoapps/debug/management/commands/dump_xml_courses.py
index f0834282b7..571ba59aa9 100644
--- a/lms/djangoapps/debug/management/commands/dump_xml_courses.py
+++ b/lms/djangoapps/debug/management/commands/dump_xml_courses.py
@@ -34,6 +34,7 @@ class Command(BaseCommand):
             default_class='xmodule.hidden_module.HiddenDescriptor',
             load_error_modules=True,
             xblock_mixins=settings.XBLOCK_MIXINS,
+            xblock_select=settings.XBLOCK_SELECT_FUNCTION,
         )
 
         export_dir = path(args[0])
diff --git a/lms/envs/acceptance.py b/lms/envs/acceptance.py
index a10ff9a164..b1d49b5237 100644
--- a/lms/envs/acceptance.py
+++ b/lms/envs/acceptance.py
@@ -34,7 +34,7 @@ DOC_STORE_CONFIG = {
 }
 
 modulestore_options = {
-    'default_class': 'xmodule.raw_module.RawDescriptor',
+    'default_class': 'xmodule.hidden_module.HiddenDescriptor',
     'fs_root': TEST_ROOT / "data",
     'render_template': 'edxmako.shortcuts.render_to_string',
 }
diff --git a/lms/envs/cms/dev.py b/lms/envs/cms/dev.py
index 0dca42f343..6fbda95ba6 100644
--- a/lms/envs/cms/dev.py
+++ b/lms/envs/cms/dev.py
@@ -23,7 +23,7 @@ FEATURES['ENABLE_LMS_MIGRATION'] = False
 META_UNIVERSITIES = {}
 
 modulestore_options = {
-    'default_class': 'xmodule.raw_module.RawDescriptor',
+    'default_class': 'xmodule.hidden_module.HiddenDescriptor',
     'fs_root': DATA_DIR,
     'render_template': 'edxmako.shortcuts.render_to_string',
 }
diff --git a/lms/envs/cms/mixed_dev.py b/lms/envs/cms/mixed_dev.py
index f636566558..0454c25409 100644
--- a/lms/envs/cms/mixed_dev.py
+++ b/lms/envs/cms/mixed_dev.py
@@ -31,7 +31,7 @@ MODULESTORE = {
                         'collection': 'modulestore',
                     },
                     'OPTIONS': {
-                        'default_class': 'xmodule.raw_module.RawDescriptor',
+                        'default_class': 'xmodule.hidden_module.HiddenDescriptor',
                         'fs_root': DATA_DIR,
                         'render_template': 'edxmako.shortcuts.render_to_string',
                     }
diff --git a/lms/envs/common.py b/lms/envs/common.py
index 42d9589401..150b9ab8b8 100644
--- a/lms/envs/common.py
+++ b/lms/envs/common.py
@@ -32,7 +32,7 @@ from .discussionsettings import *
 
 from lms.lib.xblock.mixin import LmsBlockMixin
 from xmodule.modulestore.inheritance import InheritanceMixin
-from xmodule.x_module import XModuleMixin
+from xmodule.x_module import XModuleMixin, only_xmodules
 
 ################################### FEATURES ###################################
 # The display name of the platform to be used in templates/emails/etc.
@@ -406,6 +406,14 @@ INIT_MODULESTORE_ON_STARTUP = True
 # once the responsibility of XBlock creation is moved out of modulestore - cpennington
 XBLOCK_MIXINS = (LmsBlockMixin, InheritanceMixin, XModuleMixin)
 
+# Only allow XModules in the LMS
+XBLOCK_SELECT_FUNCTION = only_xmodules
+
+# Use the following lines to allow any xblock in the LMS,
+# either by uncommenting them here, or adding them to your private.py
+# from xmodule.x_module import prefer_xmodules
+# XBLOCK_SELECT_FUNCTION = prefer_xmodules
+
 #################### Python sandbox ############################################
 
 CODE_JAIL = {
diff --git a/lms/envs/dev_mongo.py b/lms/envs/dev_mongo.py
index 3a99f44655..4d304028d7 100644
--- a/lms/envs/dev_mongo.py
+++ b/lms/envs/dev_mongo.py
@@ -19,7 +19,7 @@ MODULESTORE = {
             'collection': 'modulestore',
         },
         'OPTIONS': {
-            'default_class': 'xmodule.raw_module.RawDescriptor',
+            'default_class': 'xmodule.hidden_module.HiddenDescriptor',
             'fs_root': GITHUB_REPO_ROOT,
             'render_template': 'edxmako.shortcuts.render_to_string',
         }
diff --git a/requirements/edx/github.txt b/requirements/edx/github.txt
index d9fca2300e..19ed7b283c 100644
--- a/requirements/edx/github.txt
+++ b/requirements/edx/github.txt
@@ -15,7 +15,7 @@
 -e git+https://github.com/eventbrite/zendesk.git@d53fe0e81b623f084e91776bcf6369f8b7b63879#egg=zendesk
 
 # Our libraries:
--e git+https://github.com/edx/XBlock.git@2a1efc8a413cc140d48f33fa839143ffcbd21d83#egg=XBlock
+-e git+https://github.com/edx/XBlock.git@cd77808aadd3ea1c2027ca8c0aa5624d8ccccc52#egg=XBlock
 -e git+https://github.com/edx/codejail.git@e3d98f9455#egg=codejail
 -e git+https://github.com/edx/diff-cover.git@v0.2.6#egg=diff_cover
 -e git+https://github.com/edx/js-test-tool.git@v0.1.5#egg=js_test_tool