On: CSS Based Attack fontface

[DangerousPie]

Presumably a possible target for this would be reddit, where users can upload custom CSS to style their subreddits?

You could at least get the username, subscribed subreddits, and some debug info (such as the country code) this way...

[vuchr → DangerousPie]

They don't let you use urls. To use images in their custom stylesheet you have to upload it to reddit, then use a special code or something, that gets replaced with the image url.