When a voltage more than the rating is applied to a ceramic capacitor, which is the failure mode, a short or open?
Generally, it is a short mode when a capacitor fails due to applying an overvoltage.
However, the ability of a chip multilayer ceramic capacitor against a disruptive voltage is 5 - 10 times or more that of the rated voltage. Therefore, it is unlikely that a capacitor will fail instantly by applying a voltage slightly higher than the rated voltage.
However, when a voltage more than the rating is applied to a capacitor it is not guaranteed.