Reporting a security problem
If you find a way to harm a player, their machine or their account through Phaethon, write to hello@playphaethon.com rather than opening a public issue. Say what you found, where, and how to reproduce it, and include the version of the launcher or the runtime if it is one of those.
This covers the launcher and its installer, the runtime and its tools, playphaethon.com and its docs, the store at dl.playphaethon.com, the sign-in service at auth.playphaethon.com and the account service at api.playphaethon.com.
Every other problem
A crash, a bug, or a place where the port and the console disagree goes through the issue forms on the forge, where each kind of report has its own form.
What you can check yourself
The launcher, its installer and its updater are signed, so Windows names their publisher, and every download the launcher makes is checked against the size and the hash the store declares.