What Mistake Did Official Make?

«МойОфис» “My Office” mailing service recommended for Russian officials as the safest for business correspondence has been hacked by Mail.Ru employee Karim Valiev in 10 minutes. He made a post about it on Facebook. According to Valiev, he managed to find all vulnerable paths peculiar to mailing services in «МойОфис» “My Office” service. Later, he gave the details of his experiment to the representatives of the company.

Source: https://www.anti-malware.ru/news