Firefox Enhanced Tracking Protection breaks embeds #56
Description
Peek previews for links from Reddit, Threads, Facebook, and Instagram all fail to load in Firefox when Enhanced Tracking Protection is enabled. It shows a blank space in the embed. Ideally, Peek should show an error when the embed is blocked, and explain what happened.
There are some difficulties handling this:
- Firefox doesn't seem to have a browser or extension API to check if a given URL will be blocked.
- Peek can't hardcode the domains known to fail, because those could be modified with future Firefox updates.
- Firefox and other browsers do not allow checking the load status of an iframe (in this case, the Peek embed) as a security precaution.
Not totally sure how to work around this yet. Maybe doing a fetch() request through the background script when loading any external link, and then showing a error in the embed (or no popup at all?) if it fails. The fetch request should have error codes that the iframe does not.