Add note about permissions in ImageScaling

Author: MrTango

docs/classic-ui/images.md

@@ -106,4 +106,9 @@ up | cover
 keep | scale
 thumbnail | scale
 
-For now plone.namedfile is still expecting the direction argument with the old values.
+For now plone.namedfile is still expecting the direction argument with the old values.
+
+## Permissions
+
+The ImageScaling view is checking explicitly the permissions the current user has, in case you want to access objects which are normally not accessible to the current user, you have to override the validate_access method in ImageScale. In Products.EasyNewsletter you can find an example of that.
+