As described here, a new REST API call was introduced in JIRA 7.0 that returns properties for a given user. However, it's always returning an empty array, no matter how many properties there are.
Return a set of properties for the given user.
An empty array is returned, which means no properties have been found for the given user.
- Add a key-value pair under properties on a user profile in JIRA;
- Try to list the property keys for this user with the below REST API call;
- Observe the response returned is empty;
At this point, there's no workaround for obtaining users' properties using a REST API call.