MongoDB - query on property names

Question

I have a MongoDB collection with several documents (not all of them) of the form:

{
    "name" : "...",
    "title" : "...",
    "5411b4a0e4b0bdc638535116" : "..."
}

i.e. with an unwanted property (probably set by accident) basically having an ObjectId as name.

I'm wondering if there's a way to query all those documents. I was thinking on some kind of regex (e.g. if property name's first char is a digit), but I'm not sure this is possible at all as I couldn't find anything on this matter.

I'm using MongoDB 3.2.