signup-embeddernpm
Advisory published Updated
signup-embedder is a confirmed malicious npm package (MAL-2026-6396) that steals credentials and exfiltrates sensitive data (malicious versions 99.99.99, 99.99.99-poc2, 99.99.99-poc3). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in signup-embedder (npm)
What this malware does
[email protected] ships preinstall.js and postinstall.js lifecycle scripts that auto-execute on npm install. preinstall.js collects hostname, current working directory, pid, Node version, platform/arch, user, and the list of environment variable names, and POSTs them as JSON to https://webhook.site/f83b073c-a04a-4ac5-8930-507051bd22f7; it also performs a DNS lookup against <timestamp>.callbacks.report for out-of-band confirmation. postinstall.js POSTs a similar host fingerprint (host, cwd, pid, node, platform) to the same webhook.site URL. The package's own description and comments label it a 'HubSpot dependency confusion PoC', and the 99.99.99-poc2 version is the canonical high-version shape used to win resolution against an internal package of the same name. Regardless of the 'PoC' framing, the package is published on the public npm registry and any installer (CI, developer machine, internal build) that resolves the name will have its host identifiers and environment variable names beaconed to an attacker-controlled collector and DNS sink, enabling internal-network mapping and follow-on targeting.
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
Credential / info stealerFind it
Search your lockfiles and build artifacts for signup-embedder (3 malicious versions).
If you installed it — respond
signup-embedder is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If signup-embedder 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
- ReversingLabs · finder
Detect & block this
O3 blocks signup-embedder-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.