OpenSSF/OSV advisory MAL-2026-6822 confirms this npm version as malicious. 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.
Source
OpenSSF Malicious Packages via OSV
Summary
Malicious code in fastnodemailer (npm)
Details
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.
Decision reason
OpenSSF Malicious Packages via OSV confirms fastnodemailer@8.0.4 as malicious (MAL-2026-6822): Malicious code in fastnodemailer (npm)