Donald Trump leaked a classified Intel about ISIS to the Russians when Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergei Kislyakvisited visited the White House. According to New York times, Donald Trump told the Russians some classified information that was obtained by Israel after it hacked into a ISIS cell of bombmakers based in Syria.
According to a U.S official, the Intel that was gathered allowed the U.S to learn that ISIS was working on explosives that could fool airport security by passing as a laptop battery. The information prompted a ban of laptops from all Muslim countries coming to the United States and Britain.
The information was classified, and was shared by Israel to the United States, and was not supposed to be shared around, but Donald Trump leaked this information when the Russian diplomats came to the White House, which could then be leaked to Iran.
There has been close working relationship between the U.S and Israeli intelligence agencies, allowing for sharing of information, including the disclosure of sources and methods. The cooperation had yielded great result including the disruption of Iran nuclear program.
The American officials under former President Obama warned the Israeli intelligence to be careful of the information they shared with Donald Trump.