Key Information

• In June 2022, the Sonar Research team discovered critical code vulnerabilities in multiple encrypted email solutions, including Proton Mail, Skiff, and Tutanota.

• These privacy-oriented webmail services provide end-to-end encryption, making communications safe in transit and at rest. Our findings affect their web clients, where the messages are decrypted, mobile clients were not affected.

• The vulnerabilities would have allowed attackers to steal emails and impersonate victims if they interacted with malicious messages. Nearly 70 million users were at risk on Proton Mail alone.

• The issue has been fixed and there are no signs of in-the-wild exploitation.