Update (1055ET): Nearly an hour into the hearing, Musk tweeted a popcorn emoji. 

* * * 

Update (1047ET): Zatko told Senate Judiciary Committee members that security lapses at Twitter were so severe that they threatened national security. 

"Twitter's unsafe handling of the data of its users and its inability or unwillingness to truthfully represent issues to its board of directors and regulators have created real risk to tens of millions of Americans, the American democratic process, and America's national security," he said. 

* * * 

Update (1029ET): Twitter's former security chief turned whistleblower, Peiter "Mudge" Zatko, prepared a statement for the Senate Judiciary Committee hearing that is currently underway.