Which versions of fastify-addone are malicious?

The following npm versions of fastify-addone are flagged malicious: 5.1.0. Treat any of these as compromised.

How do I remediate fastify-addone if I installed it?

Remove fastify-addone 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.

I already installed fastify-addone — how do I know if it already compromised me?

If fastify-addone was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

Is fastify-addone part of a known attack campaign?

Yes — fastify-addone is associated with the IN-MAL-2026-009582 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find fastify-addone across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for fastify-addone (version 5.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging fastify-addone across your stack and pipelines.

Malicious package

fastify-addonenpm

Malicious code in fastify-addone (npm) Remove it immediately and rotate any exposed credentials.

MAL-2026-10098

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall fastify-addone

What this malware does

The package presents itself as fastify-plugin (name fastify-addone, repository/homepage/bugs fields point at fastify/fastify-plugin) and copies that project's source with a malicious statement inserted. lib/getPluginName.js contains a top-level statement that base64-decodes a URL via atob, fetches the JSON at https://www.jsonkeeper.com/b/HDXPP, and passes the returned content field to eval. This executes attacker-controlled JavaScript in the caller's process on any require('fastify-addone') (directly or via plugin.js). The destination is an anonymous, mutable third-party JSON-hosting service — not the publisher's infrastructure — and the payload URL is hidden behind base64 to evade casual review.

Malicious versions

1 flagged

5.1.0

Indicators of compromise (SHA-256)

21b9e477cff478ab071039c18c3adb6577a07cc1d82687b9e7d7cd2594dc9ddf

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for fastify-addone (version 5.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging fastify-addone across your stack and pipelines.
If you installed it — respond
Remove fastify-addone 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 fastify-addone was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks fastify-addone before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

Frequently asked questions

No. fastify-addone on npm has been identified as a malicious package (version 5.1.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-009582

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks fastify-addone-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.

Malware detection Runtime egress monitoring