11870.com API allows applications granted by a user to modify his profile or change his avatar. According to the document service, the user data is placed under the collection with the name "Users".
You may get the user data by accessing the url http://11870.com/api/v1/users/[user_slug], where [user_slug] is the slug the user chose when he created his account.
Normal AtomPub considerations apply.
The following attributes may appear on the Atom entry being updated:
The user avatar is placed under the link with the attribute "rel" equals to "edit-media". Normal AtomPub to manage media contents must apply here.