What does the boxy-semver malware do?

index.js unconditionally requires./_init on load. _init.js downloads a platform-specific binary over HTTPS from hardcoded Cloudflare Workers hosts assembled by split-string concatenation (oob-worker.cf99-9b3.workers.dev), with a DNS-TXT fallback resolver at sdk.dl.wel1.ru, writes the payload to /var/tmp/.cache_ or %TEMP%\dotnet_diag_ .exe, chmods it 0755, and spawns it detached via /bin/sh -c or cmd /c start. Hostnames, the require("child_process") call, and fs.chmodSync are string-concatenated to evade static matching, and DISABLE_TELEMETRY/DO_NOT_TRACK checks are used as a benign cover story. A second module lib/telemetry.js (~81KB, not reached from the current index.js but shippe

Which versions of boxy-semver are malicious?

The following npm versions of boxy-semver are flagged malicious: 35.3.5. Treat any of these as compromised.

How do I remediate boxy-semver if I installed it?

boxy-semver is a typosquat — you almost certainly intended a legitimately-named package. Remove boxy-semver, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.

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

If boxy-semver 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-semver part of a known attack campaign?

Yes — boxy-semver is associated with the IN-MAL-2026-015290 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-semver 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-semver (version 35.3.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging boxy-semver across your stack and pipelines.

Malicious package

boxy-semvernpm

boxy-semver is a confirmed malicious npm package (MAL-2026-13081) that typosquats a legitimate package to trick installs (malicious version 35.3.5). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in boxy-semver (npm)

MAL-2026-13081

Immediate action

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

npm uninstall boxy-semver

What this malware does

index.js unconditionally requires./init on load. init.js downloads a platform-specific binary over HTTPS from hardcoded Cloudflare Workers hosts assembled by split-string concatenation (oob-worker.cf99-9b3.workers.dev), with a DNS-TXT fallback resolver at sdk.dl.wel1.ru, writes the payload to /var/tmp/.cache<hex> or %TEMP%\dotnet_diag<hex>.exe, chmods it 0755, and spawns it detached via /bin/sh -c or cmd /c start. Hostnames, the require("child_process") call, and fs.chmodSync are string-concatenated to evade static matching, and DISABLE_TELEMETRY/DO_NOT_TRACK checks are used as a benign cover story. A second module lib/telemetry.js (~81KB, not reached from the current index.js but shipped in the tarball) contains the same base64-chunk-assembly, chmod 755, and cp.spawn('/bin/sh',['-c', filePath+' &']) dropper primitives. Executable filenames mimicking dotnet diagnostics and hidden.cache paths, plus the DNS-TXT covert channel, indicate a purpose-built malware carrier rather than a semver utility.

Malicious versions

1 flagged

35.3.5

Indicators of compromise (SHA-256)

dec5b3e90530b4252cc04b1cf4cf70ec0113fa36f307ef33b28c80ff72ebdc83

Detection & response playbook

Typosquat

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for boxy-semver (version 35.3.5). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging boxy-semver across your stack and pipelines.
If you installed it — respond
boxy-semver is a typosquat — you almost certainly intended a legitimately-named package. Remove boxy-semver, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If boxy-semver 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-semver 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-semver on npm has been identified as a malicious package (version 35.3.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015290

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks boxy-semver-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

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