I'm looking at the API for Feedbin (https://github.com/feedbin/feedbin-api/blob/master/content/subscriptions.md) and I can't seem to find where I can retrieve the favicon for the feed.
Does anyone know how this is usually requested?
Based on the source code, it seems to be coming from Cloudfront. Now, that probably does not answer your question as to how it ends up there. In all likely hood Feedbin or Feedly use a library that extract the favicon url based on the HTML pages related to a feed.