This happened within the last hour or so on Mi Yodeya:
The achievements drop-down is similarly affected.
This happens on every site I've tried (responsive or old design, with or without an account) except for Meta.SE, which has the correct icons.
I see that some (but not all) HNQ icons in the right column are also affected, but haven't looked for a pattern there.
I know that "meta is different", but this isn't the kind of "different" we usually see.