Twitter shareholders voted Tuesday to approve Elon Musk’s $44 billion offer to take over the company, a formal step in finalizing the disputed deal that is headed to court in October.

The vote followed Twitter whistleblower Peiter “Mudge” Zatko’s testimony Tuesday morning before the Senate, adding to his allegations of widespread security vulnerabilities that have ignited new political head winds and legal challenges for the social network.

Senate Judiciary Committee lawmakers subpoenaed Zatko to appear after they received copies of his SEC complaint, which alleges the company misled federal regulators and its own board about its weak defenses against hackers, efforts to fight spam and foreign influence operations on its platform.

Zatko’s allegations, first reported by The Washington Post and CNN, immediately reverberated on Capitol Hill, where lawmakers promised investigations and wrote letters calling the Federal Trade Commission to open a probe.

Twitter has said Zatko’s allegations appeared to be “riddled with inaccuracies,” and that security and privacy are priorities at the company.