Which versions of checkout-signer are malicious?

The following npm versions of checkout-signer are flagged malicious: 99.0.0-canary.1. Treat any of these as compromised.

How do I remediate checkout-signer if I installed it?

checkout-signer establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.

I already installed checkout-signer — how do I know if it already compromised me?

If checkout-signer 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 checkout-signer part of a known attack campaign?

Yes — checkout-signer is associated with the IN-MAL-2026-005116, IN-MAL-2026-005115 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 checkout-signer 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 checkout-signer (version 99.0.0-canary.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-signer across your stack and pipelines.

Malicious package

checkout-signernpm

checkout-signer is a confirmed malicious npm package (MAL-2026-5436) that opens a backdoor for remote access (malicious version 99.0.0-canary.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-signer (npm)

MAL-2026-5436

Immediate action

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

npm uninstall checkout-signer

What this malware does

Package replicates the API surface of an internal Exodus package (generateMnemonicSigningKeys, signDirectPaymentMultiChain, signCapture, signRefund, signCharge, signCancelSubscription exported from src/index.js), where each export throws an error rather than implementing the real signing logic. On npm install, src/canary.js (line 6) performs a DNS lookup and HTTPS GET to a hardcoded serveo.net tunnel host (https://96e03fa6c292469a-172-245-86-254.serveousercontent.com/canary-install), sending the package name and version. Any organization that pulls this from the public registry believing it to be the internal Exodus dependency reveals their install (org / CI host identification via DNS + HTTPS source) to the operator of the tunnel. README claims the package performs only a DNS lookup with no data transmission, contradicting the actual HTTPS GET with query parameters. The beacon destination is a mutable serveo tunnel pointing at a residential-style IP (172.245.86.254), which is operator-controllable infrastructure rather than a stable vendor endpoint. Regardless of any stated 'authorized research' framing, the structure — divergent-API namespace-abuse shape plus an unconsented install-time beacon to a tunneling host — is the live dependency-confusion attack pattern.

Malicious versions

1 flagged

99.0.0-canary.1

Indicators of compromise (SHA-256)

b1f3068ce30a667baae76fe67d718a1586a173eeddad17eef2347aca53bb505b

f6add4dfcaaf79ce107ac8026032b47540def183a121be2266891644c90f10c8

Detection & response playbook

Backdoor / remote access

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for checkout-signer (version 99.0.0-canary.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-signer across your stack and pipelines.
If you installed it — respond
checkout-signer establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If checkout-signer 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 checkout-signer 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. checkout-signer on npm has been identified as a malicious package (version 99.0.0-canary.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-005116IN-MAL-2026-005115

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-signer-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.

Malware detection Runtime egress monitoring

Explore

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