MalwarePublished 5 Aug 2026

cobrowsing-exception-filter (npm) · Malicious Code

Affects cobrowsing-exception-filterSource GCVE Database

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

Data as of 5 Aug 2026, 16:19 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-12654

What to do

Remove cobrowsing-exception-filter 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-exception-filter	Affected =35.8.3	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

The npm package cobrowsing-exception-filter version 35.8.3 contains malicious code that downloads and executes attacker-controlled binaries from obfuscated Cloudflare Workers subdomains and fallback DNS-TXT records. The package disguises these binaries with misleading filenames and executes them without any integrity verification. The package name suggests it is an error-handling utility, but it contains no such functionality and instead performs unauthorized code execution.

Impact

This malicious package enables remote code execution on any system that installs and requires it, allowing attackers to run arbitrary binaries with the privileges of the executing user. The lack of integrity checks and use of attacker-controlled endpoints means the payload can be changed at any time, increasing the risk of persistent compromise or further malware deployment.

Defensive guidance

Users should immediately remove version 35.8.3 of cobrowsing-exception-filter from their projects and avoid installing this package. Investigate any systems where this package was used for signs of compromise. Use trusted package sources and verify package integrity before installation.

Summary

The cobrowsing-exception-filter npm package (version 35.8.3) includes malicious code that, upon require(), loads a support script which dynamically reconstructs obfuscated endpoint hostnames controlled by attackers. It downloads opaque binary payloads to temporary directories, sets executable permissions, and runs them detached via system shells. The code uses runtime obfuscation techniques to evade static analysis and includes a rate-limiting marker and a telemetry disable flag as cover. No hash or signature verification is performed on the downloaded binaries, which are mutable and attacker-controlled. The package's declared purpose is misleading, as it contains no legitimate error-handling functionality.

References

npmjs.com/package/cobrowsing-exception-filter/v/35.8.3 (opens in a new tab)

Community reviews

Loading reviews…

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Aug 2026, 16:19 UTC

Technical details

References

Community reviews