In the month since he took office, Donald Trump has refused to drop his Samsung S3 in favor of the standard secured phone. That’s a huge security problem, since conventional phones are vulnerable to any number of outside attacks, and the US president is one of the most valuable intelligence targets in the world. But despite the real risk of compromise — which could give hackers access to the phone’s microphone and camera — Trump has continued to use the phone, sending tweets from an Android device as recently as this morning.

Now, Congress could get involved. This morning, Congressman Ted Lieu (D-CA) sent a letter to the House Oversight Committee requesting an investigation into the president’s phone and general cybersecurity practices, co-signed by 14 other members of Congress.

“The device President Trump insists on using — most likely the Samsung Galaxy S3 — has particularly well-documented vulnerabilities,” the letter reads. “What immediate actions do the President and the Office of the President intend to take to ensure the swift and safe transition of communications technologies?”

Those questions are particularly vital after an impromptu intelligence briefing at Trump’s Mar-a-Lago resort last weekend, which may have exposed sensitive documents to unsecured phone cameras. The Oversight Committee is already seeking more details into the circumstances of the briefing.

It’s not the first time Lieu has called for stricter cybersecurity in the government. In a letter to the House Administration Committee earlier this month, he drew attention to similar vulnerabilities within the House of Representatives, calling for more urgent information security training for all members of Congress, as well as a formal plan for securing members’ personal devices.