Got a 100% crash with a very specific setup in the editor.
Create a script-file with a property using a msg.url() (no other type that I know of)
Put it inside a gameobject that is in a collection.
If adding another gameobject within that gameobject (see below) and trying to view the properties of the script, the editor will freeze.
Probably has to do with a bug when populating the dropdown of urls that can be used.
Editor 1 only. Works on Editor 2 ( but for other reasons I cannot use E2 atm so I need to have this working as I want to set urls in a collection like this)
And as usual, I got a testproject if you need a full reproducable case.