Only current/last version supported.

Two ways.

1). Private vulnerability reporting GitHub feature

2). use encrypted email for send details for me.

1. Got my PGP public key: https://aminux.files.wordpress.com/2019/07/aminux-mail-pgp-public_since-2019-07-30.asc
2. Extract email from this and write encrypted email with security problem description.
3. Create issue with mark SECURITY in theme.