As this is a host your own software repository, you are responsible for the security of your hosted software, the infrastructure you host it on, and access to your software and infrastructure.
As you may be aware, critical CVEs can and do occur, for platform components, such as PHP, that are required to run this software.
You, and you alone are responsible for keeping your platform secure if you choose to utilise this software.
However, if you find a security issue in this software, any and all reports - via responsible disclosure - are welcomed.
Support will be best efforts, focussed on removal of any accidental leaking of Personally Identifiable Information (PII) that may occur.
Do not report security issues in Google Health here - report them upstream to Google - and good luck with that.
Do not report security issues in PHP or mysql here - report them upstream to PHP and mysql.
Report a vulnerability by raising an issue identifying that you have discovered a security issue, outlining the nature of the issue at the high level, or by private vulnerability reporting.