MAL-2026-12458 Malicious code in streak-calendar-core (npm)

index.mjs executes on module import and, when running inside WSL (gated on WSL_DISTRO_NAME, linux platform, and NODE_ENV!=production), fetches a remote archive from https://f004.backblazeb2.com/file/dp8hbvocjd2fpza/helper.tar.gz, extracts it via tar to /mnt/c/Users/<user>/AppData/Local/Microsoft/Windows/syscache on the Windows host filesystem, and writes an env-setup.cmd launcher into the Windows Start Menu Startup folder (AppData/Roaming/Microsoft/Windows/Start Menu/Programs/Startup/) so the dropped executable auto-runs on every Windows login. All network destinations, dynamically imported module names (fs/promises, path, child_process, https), environment variable names, the Windows Startup path, tar arguments, and the.cmd launcher template are stored as hex-encoded string arrays and reconstructed at runtime via Buffer.from(h,'hex'). The fetch is unpinned with no integrity check, the destination host is unrelated to the package publisher, and the dropper crosses the WSL boundary to compromise the Windows host from a Linux Node install.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.