mermaid-v11npm
Advisory published Updated
mermaid-v11 is a confirmed malicious npm package (MAL-2026-5539) that steals credentials and exfiltrates sensitive data (malicious versions 9999.0.0, 9999.0.1, 9999.0.2). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in mermaid-v11 (npm)
What this malware does
The package impersonates the legitimate mermaid diagramming library (name mermaid-v11, bogus version 9999.0.2, description 'Mermaid v11 diagramming library') and ships no library code — only a malicious preinstall lifecycle hook. On npm install, package.json line 6 runs node -e that reads require('os').hostname() and the OS username and beacons them out-of-band to an attacker-controlled Interactsh endpoint via two channels: an HTTPS GET to https://d8l0dj5t5p5il86s3d3gepriqucsnn1nd.oast.me/?h=<hostname>&u=<username>&pkg=mermaid-v11, and a DNS lookup of mermaid-v11.<hostname>.d8l0dj5t5p5il86s3d3gepriqucsnn1nd.oast.me to leak the hostname through the resolver chain. The behavior fires automatically on default install with no user interaction, harvesting installer host identifiers for an attacker-controlled OAST listener.
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.
The OpenSSF Package Analysis project identified 'mermaid-v11' @ 9999.0.2 (npm) as malicious.
It is considered malicious because:
- The package communicates with a domain associated with malicious activity.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Search your lockfiles and build artifacts for mermaid-v11 (3 malicious versions).
If you installed it — respond
mermaid-v11 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 mermaid-v11 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
- OpenSSF: Package Analysis · finder
Detect & block this
O3 blocks mermaid-v11-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.