Which versions of boxy-esm-shims are malicious?

The following npm versions of boxy-esm-shims are flagged malicious: 35.5.5. Treat any of these as compromised.

How do I remediate boxy-esm-shims if I installed it?

boxy-esm-shims 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.

I already installed boxy-esm-shims — how do I know if it already compromised me?

If boxy-esm-shims 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 boxy-esm-shims part of a known attack campaign?

Yes — boxy-esm-shims is associated with the IN-MAL-2026-015338 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 boxy-esm-shims 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 boxy-esm-shims (version 35.5.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging boxy-esm-shims across your stack and pipelines.

Malicious package

boxy-esm-shimsnpm

boxy-esm-shims is a confirmed malicious npm package (MAL-2026-13042) that steals credentials and exfiltrates sensitive data (malicious version 35.5.5). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in boxy-esm-shims (npm)

MAL-2026-13042

Immediate action

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

npm uninstall boxy-esm-shims

What this malware does

On require() of the package, index.js loads vendor.js which fetches an opaque binary from string-obfuscated Cloudflare Workers hosts (oob-worker.cf103-07.0.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev) with a DNS-TXT base64 fallback under *.wel1.ru (sdk.dl.wel1.ru). The downloaded bytes are written to /var/tmp or %TEMP% under a disguised name (.cache<hex> on Unix, dotnet_diag_<hex>.exe on Windows), chmodded 0755, and spawned detached via /bin/sh -c or cmd.exe with unref(). Destination hostnames and the child_process require are assembled from split string fragments via Array.join to evade static matching, and the fetch is framed as telemetry with cover-story opt-out env vars (DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, DO_NOT_TRACK). A TTL stamp file suppresses repeat execution.

Malicious versions

1 flagged

35.5.5

Indicators of compromise (SHA-256)

c8f8bbecdfed31ec416782f6de127cb1003692978560504d748acd121b30fa3b

Detection & response playbook

Credential / info stealer

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for boxy-esm-shims (version 35.5.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging boxy-esm-shims across your stack and pipelines.
If you installed it — respond
boxy-esm-shims 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 boxy-esm-shims 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 boxy-esm-shims 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. boxy-esm-shims on npm has been identified as a malicious package (version 35.5.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015338

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks boxy-esm-shims-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

Explore

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