The data of some of US President Donald Trump's closest advisers was reportedly found online by German news magazine Der Spiegel.
Included in the report were national security adviser Mike Waltz, Director of National Intelligence Tulsi Gabbard and Defense Secretary Pete Hegseth.
The officials' mobile phone numbers, email addresses and, in some cases, passwords connected to their accounts could be accessed via commercial data-search engines and hacked data widely available online.
Most of the email addresses and phone numbers found were current, the report said, with the numbers often being linked to social media accounts, as well as to accounts on messaging services such as WhatsApp and Signal.
The Spiegel report comes as the White House this week deals with the aftermath of revelations that high-ranking officials discussed plans to carry out military attacks on a messaging app.
Jeffrey Goldberg, editor-in-chief of US magazine The Atlantic, was accidentally added to a Signal group where classified details of military operations targeting the Houthi militia in Yemen were discussed by top security officials.
Security risk?
According to a technical analysis by the magazine, the wide availability of the numbers presents a security risk, with the potential of spyware being installed on the officials' phones.
The magazine also said it is conceivable that if a foreign intelligence service were to hack a phone using the data, it would likely be able access group chats like that which was used to discuss striking Yemen.
All three officials were made aware of the leaks. Der Spiegel also said it did not attempt to use any of the passwords to log in to any services.
While they did not respond to the magazine's request for comment, the National Security Council said the Waltz accounts and passwords referenced by the German magazine had all been changed in 2019.
