Better Website Security
Mozilla Observatory used to improve website security by teaching developers, system administrators, and security professionals how to configure their sites safely and securely.
https://observatory.mozilla.org/
Test Results for Protonmail website
https://observatory.mozilla.org/analyze/account.proton.me
Content Security Policy Analysis shows multiple unaddressed issues read the Full Report in the link above
Other issues found
The HTTP version of the website does not redirect to the HTTPS version. We advise to enable redirection.
Misconfiguration or weakness
Server sends useless certificates.
Misconfiguration or weakness