diff --git a/notebook/auth/login.py b/notebook/auth/login.py
index 6cf75b969..bf6c9a47a 100644
--- a/notebook/auth/login.py
+++ b/notebook/auth/login.py
@@ -25,7 +25,11 @@ class LoginHandler(IPythonHandler):
 
     def get(self):
         if self.current_user:
-            self.redirect(self.get_argument('next', default=self.base_url))
+            next_url = self.get_argument('next', default=self.base_url)
+            if not next_url.startswith(self.base_url):
+                # require that next_url be absolute path within our path
+                next_url = self.base_url
+            self.redirect(next_url)
         else:
             self._render()
     
@@ -47,8 +51,12 @@ class LoginHandler(IPythonHandler):
             else:
                 self._render(message={'error': 'Invalid password'})
                 return
-
-        self.redirect(self.get_argument('next', default=self.base_url))
+        
+        next_url = self.get_argument('next', default=self.base_url)
+        if not next_url.startswith(self.base_url):
+            # require that next_url be absolute path within our path
+            next_url = self.base_url
+        self.redirect(next_url)
     
     @classmethod
     def get_user(cls, handler):
diff --git a/notebook/base/handlers.py b/notebook/base/handlers.py
index 83cc41335..3ca50a46f 100644
--- a/notebook/base/handlers.py
+++ b/notebook/base/handlers.py
@@ -40,16 +40,24 @@ sys_info = json.dumps(get_sys_info())
 
 class AuthenticatedHandler(web.RequestHandler):
     """A RequestHandler with an authenticated user."""
+    
+    @property
+    def content_security_policy(self):
+        """The default Content-Security-Policy header
+        
+        Can be overridden by defining Content-Security-Policy in settings['headers']
+        """
+        return '; '.join([
+            "frame-ancestors 'self'",
+            # Make sure the report-uri is relative to the base_url
+            "report-uri " + url_path_join(self.base_url, csp_report_uri),
+        ])
 
     def set_default_headers(self):
         headers = self.settings.get('headers', {})
 
         if "Content-Security-Policy" not in headers:
-            headers["Content-Security-Policy"] = (
-                    "frame-ancestors 'self'; "
-                    # Make sure the report-uri is relative to the base_url
-                    "report-uri " + url_path_join(self.base_url, csp_report_uri) + ";"
-            )
+            headers["Content-Security-Policy"] = self.content_security_policy
 
         # Allow for overriding headers
         for header_name,value in headers.items() :
@@ -301,7 +309,22 @@ class IPythonHandler(AuthenticatedHandler):
             html = self.render_template('error.html', **ns)
         
         self.write(html)
-        
+
+
+class APIHandler(IPythonHandler):
+    """Base class for API handlers"""
+    
+    @property
+    def content_security_policy(self):
+        csp = '; '.join([
+                super(APIHandler, self).content_security_policy,
+                "default-src 'none'",
+            ])
+        return csp
+    
+    def finish(self, *args, **kwargs):
+        self.set_header('Content-Type', 'application/json')
+        return super(APIHandler, self).finish(*args, **kwargs)
 
 
 class Template404(IPythonHandler):
@@ -364,6 +387,7 @@ def json_errors(method):
         try:
             result = yield gen.maybe_future(method(self, *args, **kwargs))
         except web.HTTPError as e:
+            self.set_header('Content-Type', 'application/json')
             status = e.status_code
             message = e.log_message
             self.log.warn(message)
@@ -371,6 +395,7 @@ def json_errors(method):
             reply = dict(message=message, reason=e.reason)
             self.finish(json.dumps(reply))
         except Exception:
+            self.set_header('Content-Type', 'application/json')
             self.log.error("Unhandled error in API request", exc_info=True)
             status = 500
             message = "Unknown server error"
@@ -393,7 +418,7 @@ def json_errors(method):
 # to minimize subclass changes:
 HTTPError = web.HTTPError
 
-class FileFindHandler(web.StaticFileHandler):
+class FileFindHandler(IPythonHandler, web.StaticFileHandler):
     """subclass of StaticFileHandler for serving files from a search path"""
     
     # cache search results, don't search for files more than once
@@ -447,7 +472,7 @@ class FileFindHandler(web.StaticFileHandler):
         return super(FileFindHandler, self).validate_absolute_path(root, absolute_path)
 
 
-class ApiVersionHandler(IPythonHandler):
+class APIVersionHandler(APIHandler):
 
     @json_errors
     def get(self):
@@ -518,5 +543,5 @@ path_regex = r"(?P<path>(?:(?:/[^/]+)+|/?))"
 
 default_handlers = [
     (r".*/", TrailingSlashHandler),
-    (r"api", ApiVersionHandler)
+    (r"api", APIVersionHandler)
 ]
diff --git a/notebook/services/config/handlers.py b/notebook/services/config/handlers.py
index b4d72fe66..017c2c8ec 100644
--- a/notebook/services/config/handlers.py
+++ b/notebook/services/config/handlers.py
@@ -9,9 +9,9 @@ import errno
 from tornado import web
 
 from ipython_genutils.py3compat import PY3
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import APIHandler, json_errors
 
-class ConfigHandler(IPythonHandler):
+class ConfigHandler(APIHandler):
     SUPPORTED_METHODS = ('GET', 'PUT', 'PATCH')
 
     @web.authenticated
diff --git a/notebook/services/contents/handlers.py b/notebook/services/contents/handlers.py
index 035e0ed36..2a0a4cca5 100644
--- a/notebook/services/contents/handlers.py
+++ b/notebook/services/contents/handlers.py
@@ -14,7 +14,7 @@ from notebook.utils import url_path_join, url_escape
 from jupyter_client.jsonutil import date_default
 
 from notebook.base.handlers import (
-    IPythonHandler, json_errors, path_regex,
+    IPythonHandler, APIHandler, json_errors, path_regex,
 )
 
 
@@ -78,7 +78,7 @@ def validate_model(model, expect_content):
             )
 
 
-class ContentsHandler(IPythonHandler):
+class ContentsHandler(APIHandler):
 
     SUPPORTED_METHODS = (u'GET', u'PUT', u'PATCH', u'POST', u'DELETE')
 
@@ -260,7 +260,7 @@ class ContentsHandler(IPythonHandler):
         self.finish()
 
 
-class CheckpointsHandler(IPythonHandler):
+class CheckpointsHandler(APIHandler):
 
     SUPPORTED_METHODS = ('GET', 'POST')
 
@@ -289,7 +289,7 @@ class CheckpointsHandler(IPythonHandler):
         self.finish(data)
 
 
-class ModifyCheckpointsHandler(IPythonHandler):
+class ModifyCheckpointsHandler(APIHandler):
 
     SUPPORTED_METHODS = ('POST', 'DELETE')
 
diff --git a/notebook/services/kernels/handlers.py b/notebook/services/kernels/handlers.py
index a99e87579..863aa7fd8 100644
--- a/notebook/services/kernels/handlers.py
+++ b/notebook/services/kernels/handlers.py
@@ -16,12 +16,12 @@ from jupyter_client.jsonutil import date_default
 from ipython_genutils.py3compat import cast_unicode
 from notebook.utils import url_path_join, url_escape
 
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import IPythonHandler, APIHandler, json_errors
 from ...base.zmqhandlers import AuthenticatedZMQStreamHandler, deserialize_binary_message
 
 from jupyter_client import protocol_version as client_protocol_version
 
-class MainKernelHandler(IPythonHandler):
+class MainKernelHandler(APIHandler):
 
     @web.authenticated
     @json_errors
@@ -49,7 +49,7 @@ class MainKernelHandler(IPythonHandler):
         self.finish(json.dumps(model))
 
 
-class KernelHandler(IPythonHandler):
+class KernelHandler(APIHandler):
 
     SUPPORTED_METHODS = ('DELETE', 'GET', 'OPTIONS')
 
@@ -76,7 +76,7 @@ class KernelHandler(IPythonHandler):
         self.finish()
 
 
-class KernelActionHandler(IPythonHandler):
+class KernelActionHandler(APIHandler):
 
     @web.authenticated
     @json_errors
diff --git a/notebook/services/kernels/tests/test_kernels_api.py b/notebook/services/kernels/tests/test_kernels_api.py
index 0bc545c5d..eb6c36d64 100644
--- a/notebook/services/kernels/tests/test_kernels_api.py
+++ b/notebook/services/kernels/tests/test_kernels_api.py
@@ -69,7 +69,8 @@ class KernelAPITest(NotebookTestBase):
 
         self.assertEqual(r.headers['Content-Security-Policy'], (
                             "frame-ancestors 'self'; "
-                            "report-uri /api/security/csp-report;"
+                            "report-uri /api/security/csp-report; "
+                            "default-src 'none'"
         ))
 
     def test_main_kernel_handler(self):
@@ -82,7 +83,8 @@ class KernelAPITest(NotebookTestBase):
 
         self.assertEqual(r.headers['Content-Security-Policy'], (
                             "frame-ancestors 'self'; "
-                            "report-uri /api/security/csp-report;"
+                            "report-uri /api/security/csp-report; "
+                            "default-src 'none'"
         ))
 
         # GET request
diff --git a/notebook/services/kernelspecs/handlers.py b/notebook/services/kernelspecs/handlers.py
index 57338de22..c033e7ce7 100644
--- a/notebook/services/kernelspecs/handlers.py
+++ b/notebook/services/kernelspecs/handlers.py
@@ -13,7 +13,7 @@ pjoin = os.path.join
 
 from tornado import web
 
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import APIHandler, json_errors
 from ...utils import url_path_join
 
 def kernelspec_model(handler, name):
@@ -43,7 +43,7 @@ def kernelspec_model(handler, name):
         )
     return d
 
-class MainKernelSpecHandler(IPythonHandler):
+class MainKernelSpecHandler(APIHandler):
     SUPPORTED_METHODS = ('GET', 'OPTIONS')
 
     @web.authenticated
@@ -70,7 +70,7 @@ class MainKernelSpecHandler(IPythonHandler):
         self.finish()
 
 
-class KernelSpecHandler(IPythonHandler):
+class KernelSpecHandler(APIHandler):
     SUPPORTED_METHODS = ('GET',)
 
     @web.authenticated
diff --git a/notebook/services/nbconvert/handlers.py b/notebook/services/nbconvert/handlers.py
index f23ddc92b..7b55bdc2b 100644
--- a/notebook/services/nbconvert/handlers.py
+++ b/notebook/services/nbconvert/handlers.py
@@ -2,9 +2,9 @@ import json
 
 from tornado import web
 
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import APIHandler, json_errors
 
-class NbconvertRootHandler(IPythonHandler):
+class NbconvertRootHandler(APIHandler):
     SUPPORTED_METHODS = ('GET',)
 
     @web.authenticated
diff --git a/notebook/services/security/handlers.py b/notebook/services/security/handlers.py
index f182a0e2b..c34ddf9ab 100644
--- a/notebook/services/security/handlers.py
+++ b/notebook/services/security/handlers.py
@@ -5,10 +5,10 @@
 
 from tornado import gen, web
 
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import APIHandler, json_errors
 from . import csp_report_uri
 
-class CSPReportHandler(IPythonHandler):
+class CSPReportHandler(APIHandler):
     '''Accepts a content security policy violation report'''
     @web.authenticated
     @json_errors
diff --git a/notebook/services/sessions/handlers.py b/notebook/services/sessions/handlers.py
index 3ecb670d5..888d518e9 100644
--- a/notebook/services/sessions/handlers.py
+++ b/notebook/services/sessions/handlers.py
@@ -10,13 +10,13 @@ import json
 
 from tornado import web
 
-from ...base.handlers import IPythonHandler, json_errors
+from ...base.handlers import APIHandler, json_errors
 from jupyter_client.jsonutil import date_default
 from notebook.utils import url_path_join, url_escape
 from jupyter_client.kernelspec import NoSuchKernel
 
 
-class SessionRootHandler(IPythonHandler):
+class SessionRootHandler(APIHandler):
 
     @web.authenticated
     @json_errors
@@ -74,7 +74,7 @@ class SessionRootHandler(IPythonHandler):
         self.set_header('Access-Control-Allow-Headers', 'accept, content-type')
         self.finish()
 
-class SessionHandler(IPythonHandler):
+class SessionHandler(APIHandler):
 
     SUPPORTED_METHODS = ('GET', 'PATCH', 'DELETE')
 
diff --git a/notebook/terminal/api_handlers.py b/notebook/terminal/api_handlers.py
index 6895e7188..a7be0ae51 100644
--- a/notebook/terminal/api_handlers.py
+++ b/notebook/terminal/api_handlers.py
@@ -1,9 +1,9 @@
 import json
 from tornado import web, gen
-from ..base.handlers import IPythonHandler, json_errors
+from ..base.handlers import APIHandler, json_errors
 from ..utils import url_path_join
 
-class TerminalRootHandler(IPythonHandler):
+class TerminalRootHandler(APIHandler):
     @web.authenticated
     @json_errors
     def get(self):
@@ -19,7 +19,7 @@ class TerminalRootHandler(IPythonHandler):
         self.finish(json.dumps({'name': name}))
 
 
-class TerminalHandler(IPythonHandler):
+class TerminalHandler(APIHandler):
     SUPPORTED_METHODS = ('GET', 'DELETE')
 
     @web.authenticated