Which versions of cobrowsing-exception-filter are malicious?

The following npm versions of cobrowsing-exception-filter are flagged malicious: 35.8.3. Treat any of these as compromised.

How do I remediate cobrowsing-exception-filter if I installed it?

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

If cobrowsing-exception-filter 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-exception-filter part of a known attack campaign?

Yes — cobrowsing-exception-filter is associated with the IN-MAL-2026-015119 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-exception-filter 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-exception-filter (version 35.8.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging cobrowsing-exception-filter across your stack and pipelines.

Malicious package

cobrowsing-exception-filternpm

cobrowsing-exception-filter is a confirmed malicious npm package (MAL-2026-12654) that executes malicious code on install (malicious version 35.8.3). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in cobrowsing-exception-filter (npm)

MAL-2026-12654

Immediate action

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

npm uninstall cobrowsing-exception-filter

What this malware does

On require() of cobrowsing-exception-filter, index.js unconditionally loads support.js, which selects a platform-specific endpoint from a hardcoded list of obfuscated hosts (Cloudflare Workers subdomains such as oob-worker.cf*.workers.dev, with a DNS-TXT fallback under *.dl.wel1.ru). The endpoint hostnames are reassembled at runtime from split fragments (e.g. ["oob-worker.cf100-416.workers.de","v"].join("") and ["sdk.dl.wel1.r","u"].join("")) to evade static analysis. The code downloads opaque bytes, writes them to /var/tmp or %TEMP% under disguised filenames (.cache<hex>, dotnet_diag_<hex>.exe), chmods 0755, and spawns the binary detached via /bin/sh or cmd.exe. A TTL marker (analytics_state) rate-limits re-execution, and a DISABLE_TELEMETRY gate is used as cover-story framing. No hash/signature verification is performed, the hosts are attacker-controlled and mutable, and neither the fetched bytes nor the sibling 81KB lib/telemetry.js match any declared library purpose. The package name suggests an error-handling utility, but the shipped code has no such functionality.

Malicious versions

1 flagged

35.8.3

Indicators of compromise (SHA-256)

715fc9a652bf5d69755ea21ef2a906c318c511fe433df0721a13e266c3646832

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-exception-filter (version 35.8.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging cobrowsing-exception-filter across your stack and pipelines.
If you installed it — respond
Remove cobrowsing-exception-filter 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-exception-filter 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-exception-filter 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-exception-filter on npm has been identified as a malicious package (version 35.8.3 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015119

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks cobrowsing-exception-filter-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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