MalwarePublished 5 Aug 2026

cobrowsing-utils (npm) · Malicious Code

Affects cobrowsing-utilsSource GCVE Database

Malicious package : remove cobrowsing-utils and rotate any secrets on hosts that installed it.

Data as of 5 Aug 2026, 16:21 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-12659

What to do

Remove cobrowsing-utils from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

Product	Affected	Fixed in
npmcobrowsing-utils	Affected =35.7.3	Fixed in–

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Description

The npm package cobrowsing-utils version 35.7.3 contains malicious code that executes a binary dropper as a side effect of importing the package. This dropper fetches a platform-specific binary from Cloudflare Workers hostnames or, if that fails, retrieves it via a covert DNS-TXT channel from *.dl.wel1.ru subdomains. The binary is saved under disguised filenames in temporary directories, given executable permissions, and launched detached from the main process. The package falsely advertises itself as shared utilities, but the fetched binary is unrelated to its stated purpose.

Impact

This malicious package can execute arbitrary binaries on the host system without user consent, potentially leading to unauthorized code execution, persistence, and further compromise. The use of covert DNS channels and disguised filenames increases stealth, complicating detection and response. The impact includes possible system takeover or data compromise depending on the payload delivered by the dropper.

Defensive guidance

Users should avoid using cobrowsing-utils version 35.7.3 and remove it from their environments. Verify dependencies to ensure this malicious package is not included transitively. Monitor package sources carefully and prefer trusted, verified packages.

Summary

The cobrowsing-utils npm package version 35.7.3 includes code that automatically runs a main() function upon import. This function constructs Cloudflare Workers hostnames to download a platform-specific binary via HTTPS. If the HTTPS fetch fails, it uses a fallback covert channel by querying DNS TXT records from *.dl.wel1.ru subdomains to reconstruct and decode a payload. The binary is written to temporary directories with names mimicking legitimate telemetry files, made executable, and executed detached from the parent process. This behavior indicates the package is a malicious dropper distributing unauthorized binaries under the guise of a utility package.

References

npmjs.com/package/cobrowsing-utils/v/35.7.3 (opens in a new tab)

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What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Aug 2026, 16:21 UTC

Technical details

References

Community reviews