ac_calendar_tsnpm
Advisory published Updated
ac_calendar_ts is a confirmed malicious npm package (MAL-2026-5434) that steals credentials and exfiltrates sensitive data (malicious version 99.99.100). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in ac_calendar_ts (npm)
What this malware does
On npm install, the package's canary.js postinstall script issues an HTTP GET to http://157.230.17.236/dc carrying the installer's os.hostname(), package name, version, a fixed nonce, and a phase identifier. The destination is a hardcoded bare IP over plain HTTP with no opt-in, no documented purpose, and no relationship to any declared package functionality. The package describes itself as a 'dependency-confusion canary,' which matches the pattern used to enumerate internal networks that resolved a public name — the installer's host identifier is exfiltrated to an external operator without consent. The version number (99.99.100) is also consistent with dependency-confusion targeting, in which an attacker publishes an artificially high version under a name expected to exist in a private registry.
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 ac_calendar_ts (version 99.99.100).
If you installed it — respond
ac_calendar_ts 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 ac_calendar_ts 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 ac_calendar_ts-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.