The launch pad umbilical cords supply propellant to the rocket, and will definitely have some remaining at the time of liftoff.
I remember the Saturn V footage wherein a heavy protection door slams in front of the cord to protect it from exhaust plume (12:40 at this Curious Droid’s video link - How did NASA get those great film shots of Apollo and... ).
But take the Electron Rocket’s launch, where the umbilical cord, presumably LOx line, is left dangling.
How are these lines protected from catching fire, when the hot exhaust gases hit them?
Has there been any incident in past where the umbilical cord caught on fire?