Other forms: hot potatoes
A controversial subject that no one wants to talk about is one kind of hot potato. A hot potato is an issue that makes everyone feel uncomfortable.
The phrase hot potato comes up a lot in politics. For example, a reporter might explain that a candidate won't speak about a controversial topic because it's "a political hot potato," or an issue that people disagree strongly about. Hot potato comes from the idea of passing a literal hot baked potato from one person to another — no one wants to be left holding it for very long, because it will burn their fingers.