Which versions of cobrowsing-utils are malicious?

The following npm versions of cobrowsing-utils are flagged malicious: 35.7.3. Treat any of these as compromised.

How do I remediate cobrowsing-utils if I installed it?

Remove cobrowsing-utils 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 cobrowsing-utils — how do I know if it already compromised me?

If cobrowsing-utils 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 cobrowsing-utils part of a known attack campaign?

Yes — cobrowsing-utils is associated with the IN-MAL-2026-015111 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 cobrowsing-utils 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 cobrowsing-utils (version 35.7.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging cobrowsing-utils across your stack and pipelines.

Malicious package

cobrowsing-utilsnpm

cobrowsing-utils is a confirmed malicious npm package (MAL-2026-12659) that executes malicious code on install (malicious version 35.7.3). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in cobrowsing-utils (npm)

MAL-2026-12659

Immediate action

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

npm uninstall cobrowsing-utils

What this malware does

[email protected] executes a binary dropper as a side effect of requiring the package. index.js loads helpers.js which auto-runs main() at import time. main() assembles Cloudflare Workers hostnames from split string fragments (e.g. oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf102-baf.workers.dev), fetches a platform-specific binary via https.get, writes it to /var/tmp or %TEMP% under masquerading names (.cache<hex>, dotnet_diag_<hex>.exe, analytics_state), chmods 0755, and spawns it detached via /bin/sh -c "<path> &" or cmd.exe /c start /b. When HTTPS fetch fails, the code falls back to a DNS-TXT covert channel: it queries c.<domain> under *.dl.wel1.ru subdomains (sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru) for a chunk count, reassembles indexed TXT records, base64-decodes the payload, writes it to disk, and executes it. Hostnames, discovery domains, file names, and function identifiers are chosen to blend with legitimate telemetry (_l, _p, activate, analytics_state, dotnet_diag). The package advertises itself as shared utilities; the fetched binary has no relation to that stated purpose.

Malicious versions

1 flagged

35.7.3

Indicators of compromise (SHA-256)

a369ea5eb28ebfd7fddb1c5baa3fc22fb371761839c0a2bd7123df273acd2077

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 cobrowsing-utils (version 35.7.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging cobrowsing-utils across your stack and pipelines.
If you installed it — respond
Remove cobrowsing-utils 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 cobrowsing-utils 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 cobrowsing-utils 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. cobrowsing-utils on npm has been identified as a malicious package (version 35.7.3 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015111

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks cobrowsing-utils-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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