Fix WebDAV traversal

Fix a traversal error that happens when traversing a WebDAV resource and the virtual host monster is used.

Fixes #195

news/195.bugfix

@@ -0,0 +1,2 @@
+Fix a traversal error that happens when traversing a WebDAV resource and the virtual host monster is used.
+[ale-rt]

plone/dexterity/browser/traversal.py

@@ -4,6 +4,7 @@
 from plone.dexterity.filerepresentation import FolderDataResource
 from plone.dexterity.interfaces import DAV_FOLDER_DATA_ID
 from plone.dexterity.interfaces import IDexterityContent
+from Products.SiteAccess.VirtualHostMonster import VirtualHostMonster
 from webdav.NullResource import NullResource
 from zope.component import adapter
 from zope.publisher.interfaces.browser import IBrowserRequest
@@ -38,7 +39,15 @@ def publishTraverse(self, request, name):
 
         defaultTraversal = super().publishTraverse(request, name)
 
-        # If this is a WebDAV PUT/PROPFIND/PROPPATCH request, don't acquire
+        if isinstance(defaultTraversal, VirtualHostMonster):
+            # If we are traversing to a VHM, we want to just return it immediately.
+            # For WebDAV requests, the check that controls if the parent
+            # of the traversed object is the same as the context
+            # will most probably fail because VHM parent will usually be
+            # the Zope App object.
+            return defaultTraversal
+
+        # If this is a WebDAV PUT/PROPFIN1D/PROPPATCH request, don't acquire
         # things. If we did, we couldn't create a new object with PUT, for
         # example, because the acquired object would shadow the NullResource