(NewsNation) — A former Twitter executive-turned-whistleblower told Congress on Tuesday the company employed “at least one agent” from China’s intelligence and that the company knowingly allowed India to add agents to the company roster as well, potentially giving those nations access to sensitive data about its users.

That was among the revelations detailed by Peiter “Mudge” Zatko, who appeared before the Senate Judiciary Committee to lay out claims about Twitter’s security protocols. Zatko is a famed hacker who served as Twitter’s head of security until his firing last year.

He told lawmakers that the social media platform is plagued by weak cyber defenses that make it vulnerable to exploitation by “teenagers, thieves and spies” and put the privacy of its users at risk.

“I am here today because Twitter leadership is misleading the public, lawmakers, regulators and even its own board of directors,” Zatko said as he began his sworn testimony.

His testimony came as Twitter and Tesla CEO Elon Musk head to trial next month over whether Musk’s $44 billion offer to buy Twitter should be completed. Twitter shareholders on Tuesday voted to approve the takeover.

The San Francisco-based company sued Musk for terminating the agreement, while the Tesla chief executive countersued, accusing Twitter of misrepresenting the number of false and spam accounts on its service.

A Delaware judge ruled last week that Musk may include Zatko’s whistleblower claims in his case against Twitter, but denied his request to delay the trial.

In a statement, Twitter responded to Zatko’s Tuesday claims by saying its hiring process is “independent of any foreign influence” and access to data is managed through a host of measures, including background checks, access controls, and monitoring and detection systems and processes.

Sen. Dick Durbin, an Illinois Democrat who heads the Judiciary Committee, said Zatko has detailed flaws “that may pose a direct threat to Twitter’s hundreds of millions of users as well as to American democracy.”

“Twitter is an immensely powerful platform and can’t afford gaping vulnerabilities,” he said.

Zatko said that in the week before he was fired from Twitter, he learned the FBI told the company an agent of China’s Ministry of State Security, or MSS, the country’s main espionage agency, was on the payroll at Twitter.

The committee also questioned Zatko on his claims that Twitter misled regulators about its compliance with a 2011 settlement with the Federal Trade Commission over improper handling of user data.

Since then, Twitter has made “little meaningful progress on basic security, integrity and privacy systems,” Zatko’s complaint filed with regulators in July said.

Twitter has said Zatko was fired for “ineffective leadership and poor performance,” and that his allegations appeared designed to harm Twitter.

The Associated Press and Reuters contributed to this report.