When acting U.S. Ambassador to Ukraine William Taylor revealed on Wednesday that U.S. Ambassador to the European Union Gordon Sondland called President Trump from Kyiv while sitting in a restaurant, it left many former security officials dumbfounded.

Taylor testified before the House Intelligence Committee that in July, a member of his staff at the U.S. Embassy, David Holmes, "could hear President Trump on the phone," asking Sondland about "the investigations." He was referring to the request Trump made during a phone call with Ukrainian President Volodymyr Zelensky, asking him to launch an investigation into former Vice President Joe Biden and his son Hunter Biden, who once served on the board of a Ukrainian energy company. Sondland responded that "the Ukrainians were ready to move forward" with the probes, Taylor said.

This was a major violation of security protocol, Larry Pfeiffer, a former senior director of the White House Situation Room, told The Washington Post. "The security ramifications are insane — using an open cellphone to communicate with the president of the United States," he said. "In a country that is so wired with Russian intelligence, you can almost take it to the bank that the Russians were listening in on the call."

Russia has intercepted phone conversations conducted in Ukraine between U.S. diplomats and leaked the recordings. A former U.S. intelligence official told the Post that Sondland calling Trump from a restaurant is "indicative of a lack of concern for operational security," as senior officials are "routinely briefed on the threats to their communications. You could assume that talking on an unencrypted line from a foreign country would be on that list." Catherine Garcia