vybscan-testbed-obfuscated-postinstallnpm
Advisory published Updated
vybscan-testbed-obfuscated-postinstall is a confirmed malicious npm package (MAL-2026-10079) that executes malicious code on install (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in vybscan-testbed-obfuscated-postinstall (npm)
What this malware does
package.json declares a postinstall lifecycle script that runs node -e "eval(Buffer.from('<base64>','base64').toString())". Installing the package triggers execution of code that is not visible in the package source and is only materialized at install time by decoding an opaque literal. In this specific version the decoded blob is an inert console.log, but the mechanism — obfuscated-then-eval'd bytes wired into a lifecycle hook — is the canonical install-time remote-code-execution shape and has no legitimate use: it lets whoever controls the package substitute arbitrary code at install without changing readable source. The package's self-description as a testbed fixture does not neutralize the pattern; the same install-time hook would execute whatever bytes were placed in the base64 literal.
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.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Search your lockfiles and build artifacts for vybscan-testbed-obfuscated-postinstall (version 1.0.0).
If you installed it — respond
Remove vybscan-testbed-obfuscated-postinstall from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If vybscan-testbed-obfuscated-postinstall was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks vybscan-testbed-obfuscated-postinstall-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.