fix(utilities): Add atomic group in expandable field regex pattern

Replace non-capturing group with atomic group in expansion bracket regex
to prevent excessive backtracking. Add missing 'object' key to bulk view
context for template compatibility.

netbox/netbox/views/generic/bulk_views.py

@@ -258,6 +258,7 @@ class BulkCreateView(GetReturnURLMixin, BaseMultiObjectView):
     def _get_context(self, request, form, model_form):
         model = self.queryset.model
         return {
+            'object': None,
             'obj_type': model._meta.verbose_name,
             'obj_type_plural': model._meta.verbose_name_plural,
             'form': form,

netbox/utilities/forms/fields/expandable.py

@@ -59,7 +59,7 @@ class ExpandableIPNetworkField(forms.CharField):
             return [value]
 
         # Replace expansion brackets with a neutral value to get a parseable IP/CIDR
-        stripped = re.sub(r'\[[^\]]+\]', '0', value)
+        stripped = re.sub(r'(?>\[[^\]]+\])', '0', value)
         try:
             family = netaddr.IPNetwork(stripped).version
         except (netaddr.AddrFormatError, ValueError):