From ehackingnews.com
Navalny’s team is now investigating and identifying the source of the leak. The team assured them that they did not collect any personal data other than email addresses of their supporters
Attackers gained access to the email database of the “Freedom to Navalny!”(free.navalny.com), created as part of the campaign in support of the politician. The site registers supporters of the opposition leader who are ready to go out to rally. Alexei Navalny’s team promised to announce it when the number of people ready to join “at least” 500,000. The authenticity of the leaked addresses was confirmed by Ivan Zhdanov, director of the Anti-Corruption Foundation (included by the Ministry of Justice in the register of foreign agents).