The fact is that the data for access to the closed system of the medical institution was sent to the list from the Excel table in the following format:
sz.******. ru n < login> p
some recipients simply copied the received string and pasted it into the yandex search field.
The search engine also remembered these queries and when you subsequently enter the beginning of the line(for example, the site address), gave hints with the content of usernames and passwords.
Yandex has already responded to the leak and removed the relevant hints from the system.