A vulnerability in WhatsApp was abused to install surveillance malware on phones of journalists and human rights activists. To make sure that potential vulnerabilities are found quickly, the code must be open source. That's why all Tutanota clients - web, apps, desktop clients - are published under GPLv3.
https://www.washingtonpost.com/technology/2019/10/29/whatsapp-accuses-israeli-firm-helping-governments-hack-phones-journalists-human-rights-workers/
@Tutanota While privacy-focused apps should be open source, being open source itself does not ensure its privacy or security. There are more factors that can affect an application's security besides just being open source. #FOSS #privacy4everyone
