400+ Arch Linux AUR Packages Compromised in a Supply Chain Attack Deploying Infostealers
(cybersecuritynews.com)
I think there was a word missing.
To respond to what I think you were saying, this event happened in the Arch User Repository, and not the official repositories.
Arch is very clear that they are not responsible for what goes on in the AUR. For example on https://aur.archlinux.org/ :
The Debian equivalent would be somewhere between extrepo and PPAs.