Currently the "hot networks" column is showing wrong icons for some, but not all of the sites. (The URLs linked to have the correct site).
It seems to happen only on some sites -- I see it on Mathematics and Travel but not here, for example. It happens both in Firefox and Chrome for me. This screenshot is from the math.SE homepage in a fresh Chrome session. I don't usually use Chrome to access SE, so I doubt it is something getting stuck in a browser cache.
The icons for Academia, Ask Ubuntu and Ask Different are right, but "Why doesn't Cersei make peace with Jon Snow" is definitely not a Music question. Neither is "Why did Neo even have to fight?" really about Information Security ... hmm, it might be, but the actual question is on Scifi.
It also affects the navigation and global inbox dropdowns, when I view them on a site that has the problem.
The site's actual favicon is not affected.