Reportedly, a White House employee left the password in his encrypted email account at a stop in Washington.
According to the point of intersection, Ryan McEvoy left his passwords and email address on a piece of White House protonmail, decorated stationary at a bus stop near the White House.
ProtonMail is an end-to-end email encryption service, often used by political figures, journalists and others who often engage in confidential information.
It is said that a person found a note and transferred it to an online publication, which, in turn, verified its authenticity.
But the assistant, who is an assistant to the White House staff of Donald Trump, did not respond to Intercept requests for comment.
It is not clear if the error violated any confidential information.
Last week, Democrats in the House of Representatives on the intelligence committee issued a note describing the steps they would take if they were responsible for investigating Trump Russia.
They said they were interested in filing a subpoena to find out how the Trump campaign employees used the WhatsApp messaging service.
The Democrats said they want to see how a senior White House adviser Jared Kushner and other campaign members are used to messaging app and others, including iMessage, Facebook Messenger, Slack, Sign, Instagram and Snapchat on encrypted networks.
According to the publication, the committee may also consider adding ProtonMail to this list.
In September of last year, it was reported that six members of the Trump administration used private email addresses to conduct state business.
This happened after Trump and the Republicans criticized the former Democratic candidate Hillary Clinton for her use of a private mail server while working as a secretary of state.