#12058: Fix initial JSON population

netbox/extras/forms/model_forms.py

@@ -254,6 +254,15 @@ class ConfigContextForm(BootstrapMixin, forms.ModelForm):
             'tenants', 'tags',
         )
 
+    def __init__(self, *args, initial=None, **kwargs):
+
+        # Convert data delivered via initial data to JSON data
+        if initial and 'data' in initial:
+            if type(initial['data']) is str:
+                initial['data'] = json.loads(initial['data'])
+
+        super().__init__(*args, initial=initial, **kwargs)
+
 
 class ImageAttachmentForm(BootstrapMixin, forms.ModelForm):