This is security.txt document one (of two) found on protonmail.ch and was discovered five months ago.

Contact: mailto:security@protonmail.ch
Encryption: https://protonmail.com/security@protonmail.ch.txt
Policy: https://protonmail.com/blog/protonmail-bug-bounty-program/
Acknowledgments: https://protonmail.com/blog/protonmail-security-contributors/
Hiring: https://protonmail.com/careers