I recently saw a few instances of the wrong site icon showing up to certain questions in the "hot network questions" feed. Here are a few of the more, er, interesting ones:
The Workplace SE seems to be disproportionately affected, and hovering over the site icon displays the correct site name (all of the above are actually on Worldbuilding).
I can't provide steps to reproduce, but my environment is Firefox 61.0.1 on Ubuntu 16.04.
