Following up on T187617: Add security.txt to Wikimedia sites?.
https://github.com/securitytxt/security-txt
https://www.rfc-editor.org/rfc/rfc9116
The RFC has moved on a lot since 2018.
Also,
security.txt files have been implemented by Google, Facebook, GitHub, the UK government, and many other organisations. In addition, the UK’s Ministry of Justice, the Cybersecurity and Infrastructure Security Agency (US), the French government, the Italian government, the Dutch government, and the Australian Cyber Security Centre endorse the use of security.txt files.