I looked at the spec, and the receiver should be able to detect that. The holdover time should be at least 30 minutes, long enough to witness multiple signature

I looked at the spec, and the receiver should be able to detect that. The holdover time should be at least 30 minutes, long enough to witness multiple signatures come in. The timing between them is fixed, so the receiver should be able to detect the attacker slightly delaying the signals. But I certainly believe that the actual receivers might not be hardened enough for that.