You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.
mpkg123 was reported malicious
OSV:MAL-2026-3426 - Malicious code in mpkg123 (PyPI)

mpkg123
0.0.0

This version was deleted from PyPI around 2026-05-12. Installing fails with:
$ pip3 install mpkg123==0.0.0 ERROR: Could not find a version that satisfies the requirement mpkg123==0.0.0
View other deleted versions of mpkg123

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2026-05-11/ \ mpkg123==0.0.0
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)

Or, download files manually

And install manually via pip:
mpkg123-0.0.0-py3-none-any.whl (4.4KB)
mpkg123-0.0.0.tar.gz (3.8KB)