Peiter “Mudge” Zatko, the former Twitter security chief whose explosive disclosures alleged serious security flaws and misleading practices within the company, has received a subpoena to appear for a deposition in the ongoing lawsuit between Twitter and Elon Musk.

The request puts Twitter’s whistleblower at the center of Musk’s ongoing legal fight with Twitter, which he agreed to purchase in April. Musk has sought to void the deal, citing many of the same issues detailed in Zatko’s disclosures.

Zatko is scheduled to be deposed in connection with the subpoena on September 9th.

Musk’s legal team took action shortly after Zatko’s claims became public, telling reporters they were in the process of filing a subpoena as early as August 23rd. However, the documents were only officially filed on Monday, giving the request legal force and making its details public for the first time.

In an attached document (pages 11 to 14), Musk’s team details a range of documents and communications subject to the subpoena, including any materials relating to the impact of spam on Twitter’s business or referring to the notoriously troublesome mDAU figure as a “key metric.” The court will also review materials related to the end of Zatko’s employment at Twitter and his ongoing ownership of Twitter stock. Additionally, the court calls for any documents related to illegal activity by Twitter or any foreign intelligence agents employed by the company.

Zatko’s disclosures, filed with the SEC and first obtained by The Washington Post and CNN, made numerous claims of negligent security procedures and intentionally deceptive practices. Among claims made in the documents, Zatko alleges that Twitter knowingly downplayed the level of bot activity on the platform — something that Musk has cited as a central reason for attempting to back out of the deal to purchase the company.

Twitter CEO Parag Agrawal has disputed Zatko’s claims, branding them a “false narrative” in an email sent to staff and statements sent to the media. Subsequently, many leading voices in the field of cybersecurity came forward to endorse Zatko’s credentials and track record, with veteran cybersecurity journalist Kim Zetter tweeting that there was “probably no security exec with more ethics, more credibility than Mudge.”